[flakes]

I've found that when mixing the two types of routes, it can be quite easy to accidentally introduce blocking paths which freeze up the main event loop, especially if mixing async dependencies with sync ones.

When a route is async, it gets scheduled on the main event loop, meaning that any blocking calls can block all requests in flight, and block unexpected things like start up and teardown of api handlers. `asyncio.to_thread()` can help here, but it's easy to forget (and there's no warnings in case you forget).

If you do mix the two, I would be very careful to monitor the timings of your requests to detect early if blocking is occurring. For adding these metrics, I suggest using something like statsd or open-telemetry libraries for adding reporting to the endpoints, which you can feed into telemetry dashboards.