axum-impl-tower-stack

Overview

Everything routable in Axum is a tower::Service. A Router, a route, a handler-turned-service: all are Service values. Because of this, Axum inherits the entire tower and tower-http middleware ecosystem for free. A middleware is a tower::Layer that wraps a Service and produces a new one.

This skill covers the tower foundation (the Service and Layer traits), the ServiceBuilder ordering rule, the common tower-http layers and their Cargo feature flags, CorsLayer configuration, and rate limiting. The tower and tower-http API used here is stable across the Axum 0.7 and 0.8 era; code is marked // axum 0.7 / 0.8 unless a version-specific detail applies.

.layer() placement on the router (register routes before layering, .layer() vs .route_layer()) is owned by axum-impl-middleware. This skill references that rule, it does not re-teach it.