Google L4 interview experience - got the offer!

Finally got the Google offer after 2 years of trying! This was my third attempt. Sharing my experience for anyone preparing.

Round 1 - Phone Screen: Medium difficulty graph problem. BFS with some modification. Took about 30 mins.

Round 2 - Coding 1: Two sum variant but with sorted arrays and additional constraints. Had to optimize from O(n²) to O(n).

Round 3 - Coding 2: Tree problem — find LCA with some twist. This was the hardest round for me.

Round 4 - System Design: Design Google Docs collaborative editing. I talked about OT and CRDTs which seemed to impress the interviewer.

Round 5 - Behavioral: Standard googleyness questions.

Total prep time: ~6 months, ~400 problems. The key was doing fewer problems but understanding patterns deeply. AMA!