Redis Rate Limiting Solves API Spam and Scaling Gaps in Express Apps

A backend developer identified a critical vulnerability in their Express API where unrestricted endpoint access could crash servers or inflate costs from external AI service calls. In-memory request tracking was initially considered but rejected due to memory leak risks and failure to work across multiple server instances behind a load balancer. The developer implemented Redis as a centralized rate-limiting store, ensuring consistent request counts are shared across all app instances. A global limit of 100 requests per 15 minutes was applied to standard routes, while sensitive endpoints like AI generation were restricted to 5 requests per 10 minutes. The setup uses the express-rate-limit and rate-limit-redis packages with ES Modules, and Redis was noted to process limit checks in under one millisecond.