Case 2 – Identifying customer needs – Paytm

As discussed in the previous case, we learned how Airbnb created an MVP product. This MVP helped them come up with a product that customers wanted. These iterations are very important in the lifecycle of the product. A brilliantly thought, designed and implemented the product, solving no customer needs is as good as a non-existing product.

It is important to weigh your product against what customer wants continuously. Therefore, it is very important to launch your product in phases and keep gauging the customer needs. There is always a trade-off between time to market and how perfect the product is. The more time you spend on the product the better it will be but at the same time you might end up launching it late. In the meantime, your competitor might launch a product and people might get used to it. This will then make it difficult to shift customers from an existing product to yours. Hence, it’s very important to launch the right MVP. MVP should not take a lot of time to market and at the same time should also serve the customer needs.

Let’s dive into another case. This one is of a company whose number of customers sky-rocketed in a very short span of time.

Case 2 – Paytm

Paytm v1 – understanding the customer need

Everyone now knows Paytm for its wallet. But many don’t know that it didn’t start off as a wallet company.

Paytm was created for making payments online. Its name was basically chosen as Paytm as its short form of Pay through Mobile. The idea was to create a product which would provide convenience to customers for payments. India was already having a boom in the number of smartphones which customers were buying. Therefore, if you could come up with a way to have payments via those, it could definitely provide convenience to users.

One of the things which almost every customer of India was paying for was mobile recharges. Almost everyone had to recharge their mobile or pay their bill. It was highly inconvenient to do the same offline – either you had to stand in long queues or you had to search for some nearby small store to do so. In case you plan to do online, you would have to visit the operator’s site. So in case you are paying for more than 1 phone number from multiple operators, you would have to go to multiple sites and make payment.

This is the gap that Paytm decided to fill to start off. With One97 communications already running, they had the advantage of relationships with telecom providers. This helped them to come up with a product where could just come and pay for their mobile bills/recharges. The product was launched with very basic and provided customers an easy way to recharge. This product helped them get the penetration into customers mind.

The important things here to learn are below –

  1. They understood the customer need. The pain a customer has to go through to complete a bill payment or recharge.
  2. They launched a very basic product which just allowed customers to do recharges. Nothing fancy was required to validate the idea.
  3. Paytm also made sure that they didn’t take a lot of time to go to market.

Paytm Recharges MVP

Paytm v2 – building on top of MVP

Once Paytm was able to establish that customers are finding value in the product, they decided to take it further. They started other payments on their platform such as DTH etc. Influenced from Alibaba in China, Paytm decided that they should try and create a wallet system. This would allow customers to preload their money and use it for paying to merchants.

Let’s try to put this thinking into the context of what Paytm was doing. They already had solved the problem of making payments easier via mobile. But one problem still remained – each time to make a payment you had to enter your card details and then either enter OTP or your login password to complete the payment. This is where a wallet would be of great help. Customers could load enough money into their wallet and then complete 4-5 transactions directly via it. They would not have to go through the hassle of putting card details multiple times.

Paytm Wallet

Paytm understood what their customers do and what is the pain point of theirs. They understood the customer journey and also different scenarios for which customers were using Paytm.

When we talk about Paytm wallet, the biggest use case has been money transfer between users. This transfer has been made so easy. But you might be surprised to know that when Paytm decided to build their wallet, they didn’t even have P2P (peer-to-peer) transfers as the priority. Their focus was only on to create a channel for adding money into the wallet and then again taking it back to the bank. Now you might think why to focus on this, this is not even the selling point. The reason is that when you build a product it is very important to have a very strong base to it.

The base to wallet was that customers are able to add money and take it to the bank with a high success rate. P2P was an offering of wallet. Once the foundation was strongly laid, Paytm could offer P2P very easily. This then solved a lot of customers problems.

Not having the change to pay was one of the other big problem customers used to face. With P2P, people could transfer amount among each other easily. They didn’t have to worry about change anymore.

What are the learnings that we can take –

  1. Customer journey understanding is very important to further improve and innovate your product.
  2. When you plan to launch a product, its important that while you are working on it, a strong foundation is laid. A strong foundation allows the product to scale up easily and be robust in nature.
Paytm v3 – the offline mode

The next innovation which Paytm will always be remembered for is the QR. By launching wallet, Paytm had already shown that payments, on the whole, could be simplified. But the next big gap they saw was on offline stores. They realized that debit/credit cards, on the whole, were growing in the country. There were customers who would want to pay via cards and at the same time, there were stores who would want to accept the same. However, the cost of the same was high for both.

Card payment needed a connection at the merchant’s end to complete the transaction. Not every store could afford the machine and not every store had an internet connection. What was required as a solution here was something which was offline. However, most customers had internet access with them. So a solution where the customer had to be online while the merchant can be offline was needed.

Paytm launched QR. A customer had to just scan QR code and then pay. The merchant would receive an instant SMS confirming the payment and the amount received. They again brilliantly identified the gap in the market which was existing for so long and no one had tapped into.


Many people say that Paytm got lucky with demonetization. Maybe they did, but what we should appreciate is that they always identified the market gaps brilliantly. They always made sure that they act on the gap fast. They launched good MVP’s to cover the market needs.

Currently they one of the biggest payment company of India. They offer almost everything on their app. Even now they have a brilliant product strategy. With everything in one single app, they are able to up-sell and cross-sell different things to customers easily. This helps them improve their GMV, revenue and eventually profitability.

There are a lot of lessons which one can learn, but most important are –

  • Customer need identification via customer journeys and scenarios is very important.
  • MVP has to be launched into the market fast but should cover basic needs of the customer.
  • If the foundation of the product is strong it will always be robust.

Case 1 – Importance of MVP for product launch – Airbnb

You might be thinking of launching a product soon or come up with a new concept into the market. To be successful, its very important to understand the concept of MVP. You need to make sure that the MVP is launched and customers experience it. This helps in validating the idea with the potential customers.

One of the most important things is to find the right MVP. MVP doesn’t mean a product which is not even able fulfill the basic functionalities or has known bugs. Understanding and finding the right MVP for your product is very important to gauge the market.MVP

We need to break the product into smaller batches which are deliverable and also provide the right preview of the product. Continuous testing is very important to the customers. We need to have an incremental improvement of the product and the same should be validated with the customers. If we try to create the complete product in a single shot, it will always lead to a lot of deviation from the customers’ expectation. This, in turn, increases the risk of failure of the product.

Let’s dive into a case study to understand how product launches have happened for successful products.

Case 1 – Airbnb

Founding of Airbnb

Airbnb started in 2007. How it started is an even interesting story. The founders of Airbnb, Brian Chesky, and Joe Gebbia had moved to San Francisco. They didn’t have any job at that time and it became difficult for them to pay rent.

There was an industrial conference at that time in San Francisco. Almost all hotels were booked and still, people wanted the place to stay. This is when the founders saw an opportunity and bought 3 air-mattress. They thought of providing air mattress and breakfast to people. They created a basic website for people to book. And soon they had 3 people who were willing to pay and stay at their place. They charged $80 for each night.

With this idea in mind, if we think about the features of the product which will be required to launch they can be –

  • Images of the accommodation
  • Map location of the place
  • Price of the place
  • Reviews of the owner
  • Reviews of the place
  • Information on places to travel in the city/tours
  • Search functionality
  • Categorization of homes etc.

However, if we think about the most basic features which will be required to run this, they will be – images of accommodation, the location of the place, price and an ability for people to contact the place owner.

Airbnb v1 –

This gave them an idea to start this business by providing air-mattresses and breakfast. Their website allowed people to upload their place’s photos and provide shared accommodations for visitors. It was a basic website which just provided simple functionalities with location and the place.

This is how the initial website of Airbnb looked like –

Airbnb launch websiteAirbnb launch mapsAirbnb launch search

This website provided them with the validation of their idea. They now knew that there are a lot of people who want to earn extra cash and at the same time quite a lot of visitors were willing to stay at these places. They knew that they could take this idea further.

This product clearly shows the focus on the basic features and how this was used as MVP to validate the idea.

Airbnb v2 –

Even with this idea, they could not succeed. Their earnings got stagnant and they couldn’t grow. They tried to understand why more customers are not interested in these accommodations. Upon research, they found that it was due to the bad quality of images uploaded by people. This is when they decided to go around in New York City and capture photos of places themselves. This improved the quality and led to growth in revenue. Soon their business increased from $200 a week to $400 a week.

As such nothing was changed in the product, but they provided better functionality. Quality of images is a performance feature which provides more reliability to visitors about the place they will have to stay in. Since it was missing in v1, it led to stagnancy. With the improvement in this feature, the product saw growth.

Airbnb v3 –

While they were experimenting with their idea, one of the owners posted a full house as a listing. The full house listing saw a lot of interest from the people and this is when Airbnb thought of changing its focus to provide full houses to visitors. This saw tremendous growth in their business and the valuation of the firm.

The phase-wise growth of their product allowed them to change their focus from shared accommodation to full house/flat accommodations.

how Airbnb started

Since then, Airbnb has improved on all their features. Provided all the features such as great design, supplementary features such as experiences etc. Their journey is a great example of how MVP should be made and how a good MVP can lead to the success of a product.

UPI – A step towards Digital India

One of the hottest topics in India currently is UPI. Every other bank and payment provider is trying to get into UPI. So, what makes it so special? Will it really change the way payments are done in India? How secure is it?

Let’s have a look at what it actually is and how does it work.

What is UPI?

UPI stands for Unified Payments Interface. Developed by NPCI (National Payments Corporation of India), It facilitates inter-bank transactions real time. It utilizes IMPS (Immediate payment service) as a rail to transfer funds. IMPS provides the facility of transferring funds 24 x 7 (even on public holidays) from one bank account to another. In traditional IMPS, the user first had to enter the bank account number and the IFSC code and save payee (the person whom the money is being transferred to) details. After saving them, they could transfer the money after a specified cooling period of the bank.

UPI saves that pain and creates an excellent customer experience. You just need to enter the VPA (discussed later in the post) of the payee and transfer the money. No hassle of long account numbers and IFSC code search anymore.

How does UPI work – In a Nutshell

When a user registers for UPI, a VPA (Virtual Payment Address) is created for the customer. This VPA holds the identity of the bank account number and the bank IFSC code in the backend. So when a user transfers amount to the VPA of another user the money gets moved from his bank account to payee’s bank account.

UPI – Detailed Explanation


As mentioned above, UPI doesn’t use bank account details to transfer the money. It utilizes VPA. VPA is a unique id which maps to the bank account number and bank details of the user.

VPA is similar to an email id e.g. abhishek@icici or abhishek@axis. Therefore, it makes it very easy to remember and saves you from the effort of remembering the complicated bank account numbers. When you associate a VPA to your bank account, the same is validated using an OTP.

Therefore, you can create VPA for the account where you have the same mobile number as the one you use for registering in the UPI app. Based on the app, the number of VPAs you can create differ. E.g. You can create single VPA in BHIM app, while in apps like Phonepe you can create multiple VPAs associated with different accounts.

Players involved
  1. Player PSP (Payment Service Players)
  2. Payee PSP
  3. NPCI
  4. Remitter Bank
  5. Beneficiary Bank
  6. Merchants
  7. Bank A/C Holders

PSP can be either the bank themselves or other service providers like Google, BHIM etc.

How is the money actually transferred?


  1. The user opens the UPI app via their device can be Google Tez.
  2. The credentials to open the app are verified can be Touch Id or a PIN.
  3. The user then initiates a payment transaction.
  4. The credentials are then verified by the app. The user enters the UPI PIN to confirm the transaction.
  5. The Payer PSP then sends pay request to NPCI.
  6. NPCI then translates the request and resolves the VPA address of the payee. NPCI then sends this request to the payee PSP informing about the incoming payment.
  7. Payee PSP then either accepts/rejects the request.
  8. Payee PSP then informs NPCI about the acceptance/rejection.
  9. If the request is accepted by payee PSP, NPCI sends a debit request to the payer’s bank.
  10. Payer’s bank then validates the request.
  11. Payer’s bank completes the debit request.
  12. The bank then sends the response to NPCI.
  13. If the response is positive from payer’s bank, NPCI sends the credit request to payee’s bank.
  14. Payee’s bank credits the payee’s bank account with the requested amount.
  15. Payee’s bank then sends the response to NPCI.
  16. NPCI sends the response to payee’s PSP about the completion of the request.
  17. In parallel, NPCI also informs the payer’s PSP.
  18. Finally, the user’s device is notified of the completion.

How secure is UPI?

UPI is as secure as any other online bank transaction. The money transfer requires a 2-factor authentication.

  1. First, to login into the app the user has to create an authentication. It can be either a PIN or touch id.
  2. Second, to finally transfer the money the user has to enter their UPI pin.


UPI is a great step by our government to make the economy cash-free. With the government pushing for it, we can expect a lot more banks joining this rail. However, the major challenge would be to get the merchants on-boarded on UPI. Most merchants don’t want to show all their transactions on their bank statement and hence, prefer cash. Currently, the transactions made via UPI are free to the end customers. However, we will have to see how long it will remain the same.

My personal opinion is that UPI is quite simple to use and has a lot of advantages over traditional online transfers. Slowly as the penetration increases, UPI might lead the way towards making India digital.

More Reads

In case you are interested in reading further about UPI, please refer to the below pages.

  1. NPCI website
  2. Profitbooks
  3. LetsTalkPayments
  4. Medium

Swiggy Interview Experience | APM | Set 1

An Associate Product Manager is the first step towards becoming a rockstar Product Manager. Firms typically look for a candidate with the “right attitude” rather than with the “right experience” while interviewing for this position. For me, a recent MBA graduate with 5 years of operations management experience, this was truly one of the most challenging interview experience.

Interview Experience

The panel consisted of Senior Product Managers from three different teams and each took one round.

The first few questions were general and related to my work experience. After that, I was asked to frame the mathematical equation of “how to compute the SLA or the estimated time of food delivery”. The interviewers asked me this question in all three rounds as they could not exchange notes. The key to answering this question was to break down the “food delivery” path in relevant pieces and then frame the Min-Max function.

Other key questions during the interview were:

  1. What parameters would you consider in the assignment logic of delivery executive? The key to answering this question was to think from the perspective of a Delivery Boy as well as a Customer and arrive at the solution which is good for both sides. Further discussions evolved from my answer.
  2. Design the Restaurant Owner App with relevant details on which feature to prioritize and which to keep in secondary views.
  3. Missing Items are a big challenge for Swiggy. How to handle this? The key to answering this question was to break down “Missing Items” issue in several identifiable categories and frame the strategy for each leg.

One thing that went positive for me was that I was able to ask “relevant” product questions at the end. Questions like why is the consumer app designed in Restaurant-first approach and not in cuisine-first approach, etc. This will hold true for any interview- know your interviewers and ask questions which are of interests to them.


Guide to write article/interview

We would like to thank you for showing an interest in contributing to our website. It will help others learn and move up the ladder in the PM field.

Interview Guide
  1. Please use the following format for title – <Company Name> Interview Process.
  2. Please provide the details of every round you went through as part of company process.
  3. It would be helpful if you can provide a brief about your profile at the end so that readers can relate to the interview questions asked.
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  1. Feel free to write about anything relevant to the product world – it can be a new trend in the industry or a product review.
Reviewing Process
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  2. The team reviews your article and provides feedback on the article and saves your article back to draft.
  3. Please improve your article based on the feedback provided, and again submit the article for review. The status of your article becomes pending again.
  4. Finally, after you have made all the required improvements, your article gets published. Then, the status of your article becomes published.

What is BlockChain & Cryptocurrency – a simple explanation from bottom to top

What is BlockChain? In case you are too overwhelmed by all the hype around BlockChain & Bitcoin and want to understand it from a ground level. You are at the right place. Let’s start with the basics.

Every entity in this universe can be represented by numbers.

Be it the details involving sub-atomic particles of an element, or energy and gravitational forces, stars, planets; or for that matter, even humans.

The DNA is nothing but a set of codes made up of four chemical bases.

Time and again, people have thought of creating a universal system to assign a unique value to each of these entities in the universe. But the question is how do we come up with such a system that could provide a unique fingerprint to not only every transaction happening on this planet but also to things beyond humans.

The answer lies in an upcoming technology that has the potential to be a general purpose technology of our decade to fill the gap that we as humanity are suffering. The gap of trust.

Many people say that BlockChain in 2017s is what web was in the 1990s.

Is it true? Let’s leave that question to be answered by time. For now, let’s focus on understanding what BlockChain really is by starting from scratch.

SHA-256 Hash

Talking about cryptography, you must be knowing about the famous mathematician, cryptographer, scientist Alan Turing who played a great role in World War II by breaking Nazi Enigma machine that helped Allied forces get coded messages transmitted by Nazi High command for Nazi Army.

SHA-256 is one such (deterministic) cryptographic hash functions that take an input data (of any type) and returns a fixed length (256 bit / 64 characters long hexadecimal code) that serves as a unique fingerprint for the input data.

For example,

Input — Blank
SHA256 Hash- e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

Input — “hello world”
SHA256 Hash-b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9

Input — White paper on Bitcoin by Satoshi Nakamoto (creator of Bitcoin)
SHA256 Hash- dcbf274c34af14943917906e767259f7e01c05ceae4eebea39af3fd0bf32bbbd

You can use any SHA256 hash calculator for this purpose. Check —

A pretty good use of SHA256 cryptography is this famous tweet

How would this work?
John Kerry would have run the (controversial) file he had through SHA256 Algorithm to generate Hash Key.
If the hash matches with the one posted by Wiki-Leaks, he would know that the file with the WikiLeaks is authentic and it is not some false claims.


This is how a Block looks like

Data consists of all the transactions that have occurred in the particular time frame depending on the protocol the BlockChain is working on (10 mins in case of Bitcoin).

Nonce — It is an arbitrary number whose value is set so that the hash of the block (input — data + nonce) will contain a run of leading zeros (say 0000e3st4… or 000000r3jg7…) depending on the difficulty of the network protocol (higher the difficulty, more the number of leading zeros).

Let’s try to understand the concept of Nonce with a hypothetical example. Consider input data as “hello world”.

Concept of Nonce

The initial difficulty of finding a valid hash is low (starting with 0). The iteration to find the correct nonce starts with 1 and keeps on going until we get the hash value starting with 0 for 243rd iteration.

Now, the difficulty is re-adjusted to find the hash starting with ‘00’. This is achieved at iteration 1389.

Again the difficulty is re-adjusted to find the hash starting with ‘000’. This iteration goes on. Now, if the goal is to find hash starting with 4 leading zeros, then we have to iterate up to Nonce = 18014 to find first such occurrence.

Difficulty level of Bitcoin

This is the concept of mining in BlockChain. (Explained later in detail)

It is important to understand that the Hash value is unique for the combination of a nonce and input data.


Having understood what is a Block, now let’s see what is a BlockChain. In simple terms, BlockChain is a Chain of Block.


SHA256 Hash of Blocks = SHA256 (Block # + Nonce + Data (Coinbase & Transaction Lists) + Previous Block Hash + Time-Stamp)

You’ll notice that each block points to the previous block using field previous hash. That’s how the blocks are linked to form a chain.

Distributed Ledger

You must have heard — “BlockChain is a distributed ledger”. That’s because the same chain of blocks is maintained at each participating node. As shown in the above diagram, the two Nodes A & B could be located anywhere on the planet; but, they’ll always be in consensus on the blocks. This is true for a BlockChain network as big as Bitcoin or Ethereum.

Now, let’s assume there were (say) 100 nodes maintaining the ledger (the chain of blocks). Out of these 100 nodes, 10 of them shut down and connect back to the network after some time. Once back, they need to pick an active chain. However, due to technological constraints (as these nodes can be anywhere around the globe), the nodes might pick different versions of the chain as the active chain.

However, the protocol ensures that the consensus is reached quickly and the longest chain (one with the most “work”) is picked as the active chain. This chain is replicated at each node.

BlockChain is immutable
Let’s understand how.

BlockChain Immutable – any change in data changes the whole chain

Say, a hacker changed the data in Block # 2 in Node A. This would result in changing of the Hash of the block, which would change the previous hash of the next Block (Block # 3). This would further result in the change of Hash of Block # 3.

The new hash would be not valid as they do not satisfy the required Proof of Work (of getting a target hash value with leading 4 zeros).

Now the hacker would require to mine (compute new Nonce) for each block to validate the hash of all the subsequent blocks.

However, by the time the hacker mines the subsequent blocks in Node A, the chain maintained at other nodes in the network ( in this case Node B) would become longer (more “work” means more blocks) thus would by-default render the chain maintained at Node A useless (as explained in the above section of Distributed Ledger).

BlockChain Immutable – Even if a hacker makes any changes and then again mine for Nonce to correct Hash of subsequent blocks, the chain at other nodes becomes longer

Data in the Block

By now, you would have a fair idea of what a BlockChain is. However, we still need to understand how the transactions are stored in the block.

The data is stored in the format of Coinbase and Transactions of Tokens. In the below illustrated example, (say) VG is the miner who mines the Genesis block (First Block) and gets 25 tokens as the reward. This is the coinbase transaction where the person is allocated 25 tokens as a mining reward. This is how money (in form of crypto-tokens) enters the system of BlockChain.
It’s only after the tokens are allocated, can VG send transactions to any other users.
This ensures the authenticity of transactions.

Coinbase & Transaction Data

How is a Block added?

In the last section, I explained the building blocks of BlockChain. Now let’s understand how a new block is added; or specifically, what is mining?

Mining in BlockChain

Updation of Ledger
  1. Collect all the list of valid transactions from the transaction pool. Build a block containing the transactions as data. Ensure the size of the block doesn’t exceed 1MB.
  2. Calculate Hash of the block by applying SHA256 Hash function —
    SHA256(Block # + Nonce + Data (Coinbase & Transaction Lists) + Previous Block Hash + Time-Stamp)
  3. Compare the calculated hash with the target hash and check if the calculated hash is less than the target. Example, if the target hash should have 4 leading zeros, a calculated hash (say) valid. Else, Nonce is incremented and this step is repeated with the updated hash (until the calculated hash is less than the target hash).
  4. Once, the miner finds the winning block (i.e. hash less than target hash), he updated all the nodes about the block. The nodes check (for a long check-list) the winning block and if more than 50% of the nodes agree, the block is added to the existing chain and the miner gets newly created tokens as mining reward.
  5. The ledger is updated for every node.
  6. With time, as nodes with more processing power join the network, the problem can be cracked faster. However, block creation time has to be 10 minutes (as per Bitcoin protocol). Thus the difficulty of the problem is increased for every 2016th block (approx 2 weeks). With increased difficulty, the number of leading zeros in target hash increases. This requires more computational power to find the right hash.

You can see live Bitcoin transactions (in crypto format)-

BlockChain, as we understand, is an essentially a public ledger containing all the transactions. This ledger is maintained at each participating node. It’s like a shared universal truth.

What makes BlockChain Secure?

The question that should pop into our mind is if the ledger is public — What about the security of data?
There’s no reason to worry, as BlockChain uses the concept of Public-Private Keys to secure all the transaction. Let’s understand this with help of an example.

Public & Private keys are set of uniquely related cryptographic key (basically set of long random number)

Public & Private Key

Public Key is shared by everyone on a network; whereas, Private Key is kept as secret.

If anyone (even you) encrypt a file with your public key; only you can decrypt it with your private key.
If you encrypt a file with your private key, then anyone can decrypt it with your public key.

When your friend send you bitcoins (or any cryptocoins) over BlockChain, they are sending you hashed version of your Public Key, which is basically your address.
But it is signed by your friend using their Private Key so that you know that it has come from your friend (and also so to ensure no can alter the transaction).

But, the next question that should pop into your mind is how would you access the transaction if you don’t have your friend’s private key?

Let’s understand this situation and the solution with an easy example.

Say, M want to send a message to his wife W over BlockChain.

How Public & Private Key work for sending message
  1. M would encrypt the message with his Private key.
  2. M would further encrypt the resulting message with W’s public key.
  3. M receives the encrypted message and decrypts it with W’s Private Key.
  4. Since W knows the M’s public key, she decrypts the message using M’s Public Key.
  5. She receives the original message.

In this whole scenario, one has to make sure that he safeguards his private key. Else, if someone gets hold of your private key, they would be able to send your cryptocurrencies to themselves by verifying that transaction with your Private Key — in effect stealing from you!

Finally, the last attribute of BlockChain — Merkle Tree

We understand that the block that needs to be added to the chain should be less than 1 MB. How do we ensure that when there could be a huge number of transactions?

Answer — Merkle Tree.

The idea of Merkle tree is to allow you to verify the transactions included in a block, without adding each transaction in the block.

This is how it works. Let’s say there are 4 transactions that need to be added to a block.

  1. Rather than adding hash for all the 4 transactions, we first hash the leaves (transactions).
  2. We combine the hash of leaves and again run a hash function (on the combined hashed leaves) to create a first level branch
  3. We combine the hash of first level branch and then run hash function to get second level branch
  4. We go on until we get a single hash — the Root Hash

Merkel Tree | Source -

Thus, the Merkle tree creates a single value that proves the integrity of all of the transactions under it (without the need of adding all these transactions to the block).

Concept of Smart Contracts

These are IFTTT premise based programmable contract stored on BlockChain. Smart Contracts let you exchange money, property or shares based on a set of conditions (without the need of any central authority like Banks, Government Agency, Lawyer, Broker, etc). Ethereum brought the concept of Smart Contracts in BlockChain.

The smart contracts are revolutionary as it can create an autonomous decentralized system where we do not require to keep trust in a central authority to facilitate a contract.

Smart Contracts

The first real-world transaction using smart contracts was in September 2016. It was held by Barclays, Israeli tech start-up Wave and Irish dairy producer Ornua, which concluded an agreement on the supply of cheese and oil (for $100,000) to Seychelles Trading Company.

The process, which usually takes from seven to ten days, took about four hours without the need for any third-party verification.

Now, having understood how BlockChain works under the hood, lets now focus on the business implications of BlockChain.

To start with, we should understand that there are two types of BlockChain Implementation.

Public BlockChain — an Open & Anonymous (Trust-less) network in which anyone can participate. However, this kind of network would have limited value if there is no network effect.
Example Bitcoin, Etherium, etc.

Private BlockChain — a Trustful network formed by a consortium of Enterprise (to solve a particular use-case to generate shared value for themselves). The admission to this network is restricted.
Example, R3 CEV developing BlockChain solution for a consortium of Banks (using Corda), Colu, OpenChain, HyperLedger, Chain and many more.

Enterprise BlockChain Source –

Private BlockChain built with public-based architecture
Ripple is built with a public-based architecture but is privately controlled through centralized ownership to facilitate foreign payments between participating banks. It greatly reduces the operational cost of foreign remittance by providing a trusted & controlled BlockChain network to facilitate transactions (using Consensus protocol rather than Proof of Work protocol).

What makes BlockChain revolutionary?

  • Decentralized & Open
  • Immutable
  • Secure
  • Auditable — Transactional verification without central authority
  • Protection against Single point of Failure

What can BlockChain do for Businesses?

  • Facilitate instant Multi-party transactions — the best examples are from banking & payments industry — Ripple
  • Eliminate Costly Intermediaries — We are seeing usage of BlockChain in various domains as Ad-Buying (AdChain, MadHive), Loyalty (Loyyal), Music (Ujomusic, Peertracks), Content Distribution (Publiq), Advertising (BasicAttentionToken)
  • Enable Decentralized Trust — Used in Retail (Open-Bazaar), Transportation (La’Zooz), Social Media (,
  • Compliance in Supply Chain — Counterfeit protection by Alibaba Taoprotect, Walmart BlockChain implementation for Pork Compliance, Diamond Compliance by Everledger
  • Security & Tamper-proof records — Examples are Identity management (Block Verify, Civic), Health Industry (BitHealth, Nautica)

Though it is early in the development of Blockchain, the potential for incorporating the technology into almost every industry is endless.

Sharing Economy (Airbnb, Uber, OLX, etc), Crowdfunding, Governance, Supply Chain Auditing, File & Data Storage, Prediction Markets, IP & Copyright Protection, AML & KYC, Banking & Financial Markets, Health Industry, Advertising & Marketing, Land Registration and what not!

Credits – The article is inspired by the session on “Cryptocurrency & BlockChain” by Prof. Bhagwan Chaudhary (conducted by Indian School of Business).

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It gives me 🔋 to write knowing people find value in it.   

Paytm Interview Experience | PM | Set 1

Round 1 (20 mins)

After the initial shortlisting based on the resumes, there was a GD for around 20 minutes. The GD was quite systematic and almost everyone got a chance to speak.

Round 2 (45 mins)

After GD, I got shortlisted for interview.

  1. The interviewer asked me about 2-3 things which I would like to improve in the Paytm App. I told him a few things such as Paytm can customize the icons on the front of the app based on user’s usage of the app. Paytm can try and come up with a flow using which users who are offline can also pay at stores.
  2. He asked me about my internship experience. He asked me questions related to cloud. What are the different challenges the bank/insurance industry faces to move to the cloud? (I did a project on cloud procurement as part of my intern).
  3. Then, he asked me a marketing question – if you are an offline store for mobile devices, what will you do to increase your revenue. To this, I replied, that there are multiple ways I could achieve this. One can be that I give pamphlets in the newspaper in the nearby locality. Also, I could do data analysis of my past customers and understand the kind of phones being bought by people coming from different locations to my shop. Based on this I could customize my ads in the localities. I told him, that I can also go for franchise model for my shop. Another thing can be to start selling the phone accessories so that I could cross-sell to my customers and increase my revenue. Similar to these I gave some other suggestions such as up-selling to existing customers and creating a kind of loyalty program to have repeat customers at the store.

Round 3 (30 mins)

Round 3 was again an interview round.

  1. The interviewer asked me why I wanted to get into product management even though I had my internship in consulting. I told him that more than strategy ideation, I enjoy its execution as that’s where the real challenges come. I gave him some more reasons as to why I don’t like consult and was looking for only Product management role.
  2. Then he asked me if I were given a role to start as a PM which one would it be; operational, strategy or program. My reply was that I would like to start off with operational to understand the complete processes in depth and then move towards the strategy side of it. Since after understanding the operational part of the process, I would be better equipped to devise the next set of strategies for the product.
  3. Then he asked me some more behavioral questions  –
    • Regarding an instance of failure at work
    • What do I understand from product management and what do product managers do
    • What made me so excited about product management

My Profile

Placement Type – Campus
College – IIM Bangalore
Work ex – 3 yrs, Technology Analyst, Goldman Sachs (Bangalore)


Chp 4 – Product Management Interview Questions – Case Interviews

We’ll now understand how to approach Case Questions (Problem Solving Questions) and Market Sizing Questions.

You may refer to the previous chapters on –
Path to become a Product Manager
Guide on how to answer Behavioral Questions
Guide on How to answer Product Questions

The case interviews are questions where you have to perform a thorough analysis by asking right questions to isolate the precise problem, diagnose the causes and then provide a probable solution.

Let’s look at few question forms that interviewers generally ask.

Declining Profit – Sample Questions

  • You work for an e-commerce shoe company. The profits of the company have fallen this year. What could have happened?
  • You are a founder of SaaS-based Logistics solution. You see that the profits have been falling for 3 quarters. How would you find the cause? What metrics would you track?

Declining Revenue – Sample Questions

  • You are a Product Manager for a news publishing company. You notice that Advertising revenue coming from the website has fallen. What could have gone wrong?
  • You are a category manager of fashion for an e-commerce company. You notice that the sales have been falling. What would you do?
  • You own a SaaS company. You notice that subscription for a premium product has fallen but that of a standard product has increased. What might have happened?
  • You notice that revenue coming from a Google Adwords for a particular keyword has fallen in a region. Google asked you to figure out and tackle this. What would you do?

Decline in new customers / new visitors – Sample Question

  • You are a Product Manager for a salon booking company. You notice that number of new customers this month has fallen. What could be the cause? What would you do?
  • You own an affiliate website. You notice that number of new visitors coming from your site has dropped down. How would you tackle this?

Decline in traffic

  • You manage a publishing site and see that traffic has reduced by 10% this month? What could be the cause? What would you do?

Approach for answering Case Interview Question 

How to attempt Case Interviews

Framework for solving Declining Profit / Declining Revenue

Declining Profit/Revenue Framework


Framework for solving Declining Traffic / Declining Customers

Decline in Traffic Framework

Market Sizing / Estimation Questions

Answering Market Sizing / Estimation question requires two types of inputs:
Basis data — Quantitative data available from published resources or a previously conducted survey.
Relational data — The quantitative data that provides the link between the basis data and the target market size.

Market Size Estimation                                                         

There are two approaches for using the estimation (alternate)technique —
The top-down approach, where we generally consider broader data (population in a region or number of production facilities, etc) as our basis data and then postulate relational data based on fraction of the market of our interest; and vice-versa for the Bottom-Up approach.

Example of Top-Down approach: Say we want to estimate the market size of Home AC in India. This is how we estimate the market size —

Top-Down Estimation Approach                                   

Example of Bottom-Up approach: Say we want to estimate of Revenue from a Burger King Outlet. This is how we calculate the estimates —

Bottom-Up Estimation Approach
Previous Chapters –
Path to become a Product Manager
Guide on how to answer Behavioral Questions
Guide on How to answer Product Questions
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Chp 3 – Product Management Interview Questions – Product Questions

This chapter, we’ll focus on the Product Questions asked in a PM interview.

You may refer to the previous chapters on:
Understanding the path to become a Product Manager
About-Me & Behavioral Questions

Questions related to Product are core to a PM Interview.

The questions have following common forms –
1. Design: How would you design a <product >?
2. Improve: What would you improve about <product>?
3. Favorite: One <product> you like and why?
4. Product/Business Strategy
5. Metrics
: What metrics would you track for <product>?
6. Launch: How would you launch a <Product>?

Let’s understand how to answer these questions in detail.

Q Form — Design: How would you design a <product>?

What approach to take:
Step 1: Identify the users and customers who’d be using the product. Understand the well.
For example, if you are asked to design mobile app for an e-commerce seller.
Get deep into understanding your users –
Ask about what do these sellers sell?
Do the sellers sell on multiple channels?
Are the seller’s individual or enterprise sellers?

For Step 2 to 3, it would be helpful to develop a customer journey map.
Refer: PM101 – Chp 4 – How to Create Personas & User Journey Mapping?

Step 2: Understand the use-case. What are the goals of your users or customers in each phase of using the product?
Step 3: Are the users using any current product? What are the challenges faced in the current flow or by using the current product?
Step 4: What improvements would lead to a better experience for your users or customers based on their goals?
Step 5: Visualize (if possible) the design based on identified improvements.

Q Form — Improve: What would you improve about <product>?

Step 1: Understand the User and their goal.
Step 2: Understand the Product Goal.
Step 3: What are the problems that the product face currently? This can be related to product flow, lower user engagement, increasing revenue or conversions, etc.
Step 4: Brainstorm on how you can improve the product. The improvements can be bold and big as well as small and iterative. You could use –
a – Customer Journey Mapping as shown to brainstorm improvements around the current challenge
b – Focus on Usability of the product to come up with improvements
Step 5: How would you implement these improvements? Are there any technical or business constraints that you should discuss?
Step 6: How would you validate your improvements? What metrics would you track for validation?

You are asked how to improve Go-Fro website — a holiday package booking site. You could develop a customer journey which would help you answer.

Customer Journey Mapping for Go-Fro Website user

Secondly, you can focus on usability of the site as illustrated.

Focus on Usability for suggesting improvements Refer – PM101 – Chp 11 – How to conduct Usability Testing?

Q Form — Favorite: One <product> you like and why?

Step 1: Understand the User and their goal.
Step 2: Understand the Product — What problem it solves?
Step 3: How does the product solve the problems? Or How does it accomplish the user goals?
Step 4: What is great about the product — in terms of Usability? What are the “Wow” features?
Step 5: How does it compare with other alternatives?

ExampleTrello is a visual system to organize anything (Projects/Ideas/Personal Tasks) the way you want. It is a super powerful tool to make project management easy, collaborative and even fun. Let’s explore how you can use Customer Journey Mapping to answer a question on a favorite product (Trello).

Trello User Journey

Wow Features:
– Visual Appeal where user can visually see tasks rather than simple texts
– Intuitive and ease of use
– Conceptually Easy
– Flexibility to use Trello as a Project Management Tool, Week Planner, Travel Itinerary Planner, Ideas Management Tool or simply day planner

You could also rate Trello in terms of usability (using screenshots) –
Learnability — The product is pretty easy to use for any first-time user
Efficiency — User can accomplish their tasks/goals with ease and in less time
Recovery from Error — User can easily undo any changes that they make (e.g. moving a card back, or deleting any task)
Satisfaction — Going by reviews the users are pretty satisfied by Trello

Refer – PM101 – Chp 11 – How to conduct Usability Testing?

Q Form — Question on Product/Business Strategy

You should think about a Product Strategy on Micro (Product) level and Macro (How Product fits into Business Strategy) level.

Sample Questions:
– Why did MakeMyTrip and Goibibo merge?
– Why did Amazon enter into India via Junglee and why would it suspend it later?
– Why Microsoft bought LinkedIn?
– Why Flipkart bought Myntra?
– Why would Google be interested in entering into cell phone market?
– Why did Google stop shipping Google Glasses?
– Why would Facebook buy Whatsapp? What could be the possible ways to monetize Whatsapp?

You could think of following strategies which can help you answer the questions –

  • Increase addressable market
  • Synergize products to provide more value to users and complete workflow solution
  • Entering into new market
  • Reducing reliance on a Key Partner
  • Bringing a core competency in-house
  • Being a “One Stop for — ”
  • Developing Cost Leadership
  • Diversifying
  • Building Barriers for Competitors
  • Developing resource (data) to serve potential market
  • Alignment with core strategy

Frameworks to look at –
PORTER 5 Forces
Workflows for Product Synergy

Example Why Microsoft bought LinkedIn?
Microsoft has been moving from just being a productivity tool to offering a whole range of cloud service (especially for enterprises). LinkedIn brings the power of professional network which can really help Microsoft provide a differentiated cloud offering which can re-invent business processes in a whole new way.

This synergy can bring together a professional’s information on LinkedIn’s public network with the information in Office 365 and Dynamics to provide a more connected and intelligent productivity flow.

Also, it would drive better monetization through more targeted advertising.

Remember, Microsoft knows what you are working and with whom (Office 365) and what kind of people (LinkedIn network) and what information (LinkedIn news feed and Lynda) can be helpful to you.

And combine all this with Cortana!


Microsoft & LinkedIn Synergy

Q Form — Metrics: What metrics would you track for <product>?

You could read in details on how to select which metrics to measure in
PM101 – Chp 16 – What metrics to track?
PM101 – Chp 17 – Develop Product Growth Model

Step 1 — What are the business goals?
Step 2 — Identifying business metrics based on business goals e.g. CAC, LTV, MRR.
Step 3 — Identifying any North Star Metric and/or Check Metric.
Step 4 — Identifying Product metrics based on Business metrics

The two approach to defining product metrics are –

AARRR framework

AARRR Framework

HEART framework
Task Success

Sample Question
– You are launching a major change in UI of your company’s app. What metrics would you track and why?
– You are a founder of SaaS startup and have just raised capital. Your investor has asked you to develop a company health dashboard. What metrics would you choose to display on that dashboard?

Q Form — Launch: How would you launch a <Product>?

Important framework to use –
Marketing Mix — 4 Ps
5Cs (Company, Customer, c…)
Customer Purchase Decision Making

Step 1 — Understand the Target Users, their needs, and their touch-points.
Step 2 — Understand the Product Goals and what stage is the product. If initial stage, what are the Lunch Goals?
Step 3 — How will you Distribute the product? Are there any key partnerships which would help you take the product to the target audience?
Step 4 — How would you roll-out the product — Do you intend to do a private beta release first followed by public beta (invitations only)?
Step 5 — How would you Market the product? Make use of 5Cs or Customer Purchase Decision framework.
Step 6 — Talk about Monetization strategy and Pricing model.

For pricing you can refer to following:

Pricing Frameworks –
Cost-Plus Pricing
Value Pricing
Competitive Pricing
Experimental Pricing

Concept of Economic Value in Pricing

Pricing Model –
Free (Ad supported or Data as a resource for underlying service/product)
Freemium model
Free Trial
Razor & Blade

Channels for User Engagement

Sample Questions –
How would you launch a grocery app?
How would you launch a community platform for lawyers?
How would you launch an electronic product?
How would you launch an electric car in India that is thrice more efficient than any other car?
How would you launch Kindle Subscription for schools?
An example of a product that wasn’t launched well. How would you launch the same product?
How would you monetize a note taking app?
How would you monetize an app that checks your grammar?
How would you price Amazon Prime?
How would you price enterprise data backup service?

Previous Chapters –
Path to become a Product Manager
Guide on how to answer Behavioral Questions

Next Chapter –
Guide on How to approach Case-based & Market Sizing Questions

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Mockup Design

A curated list of best MockUp Design Tools & Resources

Design, CMS and Hosting all in one.
Link –

Free Mockup Generator that lets you create high-quality product mockups easily.
Link –

Drag & Drop tool for creating mockups instantly
Link –

Free Realistic mockups for website and apps
Link –


Easily Create user flows
Link –

Collection of design resources by designers at Facebook

 Link –

A popular prototyping app

Link –


A quick and simple drag and drop mockup for brainstorming at initial phase
Link –

UX inspirations for anyone
Link –

Landing Page Inspiration

Link –

More tools coming soon..