FastAPI

Production-shaped guidance. Targets FastAPI 0.115+ and Pydantic v2.

When FastAPI is the right choice

FastAPI is the default for new Python web services in 2026. It's the right pick when:

• The team is already strong in Python (ML, data, scripting heritage).
• You want async I/O (DB, HTTP calls, queues) with low ceremony.
• You want OpenAPI/JSON schema for free.
• You're building APIs, not server-rendered HTML (for that, Django still wins).

It is not magic — async Python is faster than sync Python on I/O-bound work but slower than Go/Node on raw CPU. Reach for FastAPI for the developer ergonomics; reach for Go/Rust if you're CPU-bound at the edge.

Project structure

Don't follow tutorials that put everything in main.py. Use a layout that scales: