PayU Interview Experience – Senior Software Engineer

Round 1:

1. How will you handle DDoS attack?
2. Design a login API which is secure even if SSL certificate is compromised.
3. How will you design an API whose response will have the response from 3 other different microservices?

Round 2:

1. Detect a loop in a singly linked list.
2. Find the Missing Number.
3. You are given 8 identical looking balls. One of them is heavier than the rest of the 7 (all the others weigh exactly the same). You a provided with a simple mechanical balance and you are restricted to only 2 uses. Find the heavier ball.
4. Project discussion.

Round 3:

1. Maximum Path Sum in a Binary Tree.
2. For what value of n following code does: (n & (n-1) == 0)
3. What is the Python decorator? Give an example.
4. Difference between Python 2 and 3.
5. How does OAuth 2 work? What kind of problem it’s solving?
6. OAuth 2 grant types?
7. What is the meaning of OAuth 2 token bearer?

Round 4:

1. Design a notification system for following types of notifications.
2. Low priority notification – Should be delivered within an hour.
3. Regular priority notification – Should be delivered within 30 minutes .
4. High priority notification – Should be delivered within 30 seconds .

       Note: Notification should not be delivered more than once.