LAB REPOSITORYSTARTER CODE

Sliding Window Rate Limiter

An in-memory limiter that stores recent request timestamps per key and computes allow, remaining, and retry-after decisions.

TypeScriptDifficulty: starterArchive: Design an API Rate Limiter →

$Read src/demo.ts and run it with any TypeScript runner.

Key Takeaways & Architecture Lessons

01.The key choice decides what the limiter actually protects.
02.Old hits must be evicted before checking the current request.
03.Shared production limiters usually move this state into Redis or another atomic store.

# Sliding Window Rate Limiter

This limiter keeps recent request timestamps per key and rejects calls once a key has too many hits inside the active window.

Production systems usually store this state in Redis or another shared store. The in-memory version makes the algorithm easy to see first.

Read in order:

1. `src/limiter.ts`
2. `src/demo.ts`

The demo prints numbered steps showing accepted requests, blocked requests, retry timing, and capacity returning as the window moves.