FastAPI Migration

Goal: Migrate to FastAPI for better performance, strong typing, data validation, and improved developer ergonomics. We prioritized high-traffic endpoints first and are now migrating the remainder (as of Feb 2026). Later we will migrate html pages.

Workflow

1. Create: Build the new FastAPI endpoint, ensuring it matches existing functionality.
2. Stage: Deploy to the testing environment (available at _fast/<endpoint>).
3. Route (Testing): Update testing NGINX config to point to the new endpoint.
4. Verify: Test edge cases, comparing testing traffic to production.
5. Deploy: Merge to master, update olsystem routing, and wait for deployment.
6. Cleanup: Remove old endpoints, add local redirects (deprecated_urls), and merge.