Count Events in a Trailing 15-Minute Window with a Fixed-Size Ring Buffer

Count Events in a Trailing 15-Minute Window with a Fixed-Size Ring Buffer

Company: OpenAI

Role: Software Engineer

Category: Software Engineering Fundamentals

Difficulty: hard

Interview Round: Onsite

Overview: Implement an event counter that returns how many events occurred in the trailing 15 minutes, using a fixed-size ring buffer of per-second buckets so memory stays bounded at any event rate. It tests circular buffers, stale-slot detection, window boundaries, late events and thread safety.