Middleware Cascade Overhead
warninglatencyUpdated Nov 8, 2025
Each middleware layer in FastAPI creates coroutine boundaries and adds latency overhead. Production stacks with authentication, logging, CORS, and monitoring middleware can reduce throughput by 80% compared to baseline.
How to detect:
Monitor per-request latency breakdown showing significant time (>50ms) spent in middleware processing. Compare request duration for endpoints with varying middleware stacks. Watch for increasing latency as middleware layers are added.
Recommended action:
Profile middleware execution order and timing. Consolidate middleware where possible (combine logging and metrics collection). Use structured logging with async handlers to avoid blocking. Consider implementing custom lightweight middleware instead of stacking multiple third-party solutions.