Paytm Interview Experience (5 Years Experienced)

Round 1(Coding):

1. Find the depth of JSON object.
2. Given weight X, collect maximum stones from weight 1 to X, where don’t repeat the stones which already available with you.

   Eg. X=10 and stones already available (1, 2, 5), then only two stones can be picked. (3, 4), (3, 6), (4, 6)

Round 2:

1. Given a 2D array find the sum of subarray on O(1) given the start and end coordinates of the array. You can precompute whatever you want.
2. How will you iterate over a DAG? Ignore the node if you have already visited.

Round 3:

1. Design WhatsApp.
2. Questions after designing:
3. How will you create persistent connections between the server and the client?

4. What is the algorithm you will use for the load balancer?

5. What is the technique you will use for load balancing in the database?
6. In persistent connection how will you handle rate limiting?