The Complete Guide to @hazeljs/gateway: Intelligent API Gateway for Microservices

A practical, in-depth exploration of the HazelJS API Gateway — from routing and versioning to canary deployments and production-ready patterns. Table of Contents Introduction Why an API Gateway? Architecture Overview Core Concepts Getting Started Version Routing Canary Deployments Resilience Patterns Traffic Management Production Integration Best Practices Introduction The @hazeljs/gateway package is an intelligent API gateway designed for HazelJS microservices. It sits between your clients and backend services, providing: Unified entry point — Clients talk to one URL; the gateway routes to the right service Version routing — Route by header, URI, query param, or weighted distribution Canary deployments — Gradually shift traffic with automatic promotion or rollback Resilience — Circuit breaker, rate limiting, retries, and timeouts per route Traffic mirroring — Shadow traffic to test new versions without affecting users Real-time metrics — Per-route and per-version performance tracking