SDE Path

Google Search QPS & Concurrency

Easy

Google handles 2 billion search queries per day. Average query latency is 200 ms.

Use: 1 day = 86,400 sec ≈ 10^5 sec. Powers of 10: 1 KB = 10^3 B, 1 MB = 10^6 B, 1 GB = 10^9 B, 1 TB = 10^12 B, 1 PB = 10^15 B.

Compute average QPS, peak QPS, and how many queries are in flight at once.

Back-of-envelope counts: any answer within ±30% of the target is correct, just like a real interview. Suffixes like k, M, B work.