API Gateway + Rate Limiter

A reverse proxy API gateway sitting in front of internal services, handling authentication and rate limiting centrally instead of duplicating that logic across every downstream service.

Without a central gateway, every service ends up reimplementing its own auth checks and rate limiting inconsistently — some routes unprotected, quotas untracked, and no unified view of who's hitting the API too hard.

JWT authentication middleware validates every request before it reaches a downstream service. A sliding window rate limiter backed by Redis tracks usage per user, with configurable quotas per route and per user tier, returning standard 429 responses with a Retry-After header when limits are exceeded.

• →JWT validation middleware sitting at the edge of the gateway, rejecting unauthenticated requests before any downstream call
• →Sliding window rate limiting implemented in Redis for low-latency quota checks under load
• →Per-route, per-user-tier quota configuration instead of one global limit
• →Centralized request logging with per-IP volume tracking in PostgreSQL to flag abuse patterns

Sliding window rate limiting is deceptively easy to get wrong at the boundary — a naive fixed-window implementation lets a user burst 2x their quota right at the window edge. Redis-backed sliding windows avoid that.

Centralizing auth and rate limiting in a gateway adds one more network hop and a single point that must stay highly available, in exchange for removing duplicated, inconsistent logic from every downstream service.

Unauthorized request throughput reduced by 100% via the token validation layer, with abuse patterns now visible through per-IP request volume tracking.

Add per-route circuit breaking so a struggling downstream service degrades gracefully instead of the gateway continuing to forward requests it can't fulfill.