create express app listen server app settings environment config router mounting route parameters query parameters request body response send response json

GET routes POST routes PUT routes PATCH routes DELETE routes multiple handlers route patterns express Router nested routers router param

application middleware router middleware built-in json middleware urlencoded middleware static middleware custom middleware error middleware middleware order request timing request ID logging middleware

status codes response headers redirect download sendFile content negotiation cookies clearCookie stream response ETag

input validation sanitization CORS Helmet headers rate limiting authentication middleware authorization middleware secure cookies proxy trust body size limits

database connection repository boundary async route handler transaction boundary N+1 avoidance cache layer pagination filtering sorting graceful DB shutdown

404 handler central error handler async errors validation errors route unit test integration test with Supertest mock dependency health endpoint readiness endpoint structured error response

environment variables reverse proxy trust proxy process signals graceful shutdown compression static cache headers structured logs metrics hook deployment checklist