His asyncpg example doesn't make much sense to me. What if there was a config change with a bad password? I would like to know this immediately on startup, else my rolling deploy is going to bring down all the previously well configured instances, and by the time we lazily try to connect to postgres it's too late.

I'm not a big python user, but I do find it kind of surprising there isn't an awaitable and thread safe mutex in the stdlib.