python-middleware

Standardizing FastAPI middleware ordering involves composing a single-purpose ASGI chain in LIFO registration order to ensure consistent observability, security, and error handling across asynchronous request boundaries. This approach prevents state leakage and unstructured responses.

Managing contextvars across async boundaries in Starlette requires a standardized middleware chain that maintains request-scoped state, ensuring correlation IDs persist throughout asynchronous processing for structured logging and telemetry.

Adding rate limiting and panic isolation to an ASGI application requires a structured middleware pipeline enforcing per-subject limits and recovering from panics to produce structured 500-error envelopes, preventing unhandled exceptions from crashing the service.

This middleware chain approach works with FastAPI security headers and CORS handling by integrating them into a standardized composition pipeline, ensuring secure header injection and cross-origin resource sharing policies are applied consistently across all requests.

Middleware registration order matters in FastAPI and Starlette because ASGI middleware executes in LIFO order, meaning the last registered wrapper processes requests first. Incorrect ordering causes state leakage, broken telemetry correlation, and authentication bypasses.

Generating a standardized middleware registration block for a new FastAPI service involves using this Skill to produce the composition code and corresponding implementation files, wiring up a robust request pipeline with RequestID, Recoverer, Telemetry, Logger, SecurityHeaders, Authenticate, and RateLimit layers.