Express.js Rate Limiter

express-rate-limiter is a middleware for Express.js applications designed to control and limit incoming requests based on user IP addresses. It implements a dual-tier rate limiting strategy: an 'inner limit' to prevent rapid-fire requests (hammering) and an 'outer limit' to guard against general overuse. The current stable version is 1.3.1. While the package previously removed external dependencies for its storage mechanism, it now primarily utilizes an in-memory store, with a roadmap item to support pluggable database solutions like Redis. Key differentiators include its configurable dual-limit approach and automatic inclusion of standard X-RateLimit and Retry-After HTTP headers in responses when limits are exceeded. Releases appear somewhat irregular but indicate active maintenance through minor versions.