The hidden cost of --reload in uvicorn: what actually consumes CPU in production

Mon, 04 May 2026 00:00:00 +0000

The Problem Nobody Sees
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Two months ago I deployed a FastAPI API to production and the server was behaving strangely. CPU stable at 40-50% for no apparent reason. I thought it was a memory leak, that it was the logs, that it was the database. It was --reload.

It turns out that copy-pasting the development command directly into the Docker container is more common than it should be. And yes, uvicorn with --reload works. The server responds. Requests go fast. But there’s a cost you don’t see until you have 10K requests daily.

Performance on Servicios Rogeliowar

The hidden cost of --reload in uvicorn: what actually consumes CPU in production

The Problem Nobody Sees #

The Problem Nobody Sees
#