Time-Window Counter

Published 3 October 2026

Onsite Coding Round 2 — Time-Window Counter

The second coding round combined object-oriented design with a counting problem. I needed to implement a counter class supporting put(), get_count(), and get_total_count(), with a fixed time window such as 300 seconds supplied when the class was initialized.

High-QPS Requirement

We discussed multiple possible designs, and the interviewer specifically asked me to implement the version where put() remained efficient under very high write throughput.

Production Follow-Ups

After coding, the interviewer asked how the design would change in a production environment and how I would handle concurrent or multithreaded access.