Phone screen:
First round was on 2-3 ML basics related questions a coding question related to compairing 2 nested sets and checking for equality

Onsite:
Coding 1(45 min): Find similar pins related using boards. Also find distance between 2 pins. The first one was based on Union Find and second part was on BFS. Similar problem: https://leetcode.com/problems/accounts-merge/description/

Coding 2(45 min): It was implementing a leader board for a game. It was a variation of LFU cache

ML Design 1(1hr): Design Image search system (End-end)
ML Design 2 (1hr): Design search and ranking natural langauge showing pins. Major focus on L2 ranker
Behavior (45 min): Focus on past project and behavior

Major challenge and learnings:

• Implementing and testing leetcode hard questions in 45 min, need a lot of practice writing code fast. Also writing test cases and passing them
• For system design on ranking, need deep understanding of loss functions for multi task learning, how to assign weights to loss function, how to apply position bias corrections and other loss normalizations, point wise vs pairwise loss and which to use for large scale training etc. Need very deep understanding and details on the flows