Dont rely on the builting Flask Development server.

[laundmo]

you should never serve a page thats supposed to be used with the Falsk Development server.

The development server is provided by Werkzeug for convenience, but is not designed to be particularly efficient, stable, or secure.

an alternative to Flask could be Sanic, which is similar to Flask but based on asyncio, and has a builtin server that works for deployment.