API Rate Limiting: The Feature You're Forgetting to Build

Your API is a door — rate limiting is the lock

Without rate limiting, a single bad actor (or a buggy client) can bring your entire system down. Yet most dev tutorials skip it entirely.

The sliding window technique

Track request counts per user in a Redis sorted set keyed by timestamp. Each request adds a timestamped entry; expired entries are pruned. If the count exceeds the limit, return 429 Too Many Requests.

Implementation tips

• Use middleware — Don't pollute your business logic. Express, Laravel, and Django all support middleware cleanly.
• Return Retry-After and X-RateLimit-Remaining headers so clients can back off intelligently.
• Set different limits per endpoint — login attempts need stricter limits than read-only GETs.

Rate limiting isn't just a security feature — it's reliability engineering. Build it before you need it.