The Complete Request–Response Lifecycle
Request–Response Lifecycle
A request travels through several layers before the application handler executes.
A browser or client first resolves the hostname using DNS. It establishes a TCP connection and, for HTTPS, performs a TLS handshake. The client sends an HTTP request through potentially several network components such as a CDN, load balancer, reverse proxy, or API gateway. The application authenticates and validates the request, executes business logic, accesses data, serializes a response, and sends it back.
Understanding this lifecycle is essential for debugging latency, authentication problems, proxy failures, CORS issues, and production outages.
HTTP Request Lifecycle
Key Takeaways
- An API request can pass through many layers.
- Latency is not necessarily caused by application code.
- DNS, TLS, proxies, gateways, databases, and serialization can all affect performance.