I can understand being nervous about some cron job running on some other service, but what's concerning about a cron job managed inside of Postgres with pg_cron? If that doesn't run, your database is probably down anyway.

Postgres might cost more but I'm probably already paying. I agree that exhausting connections and writing at a high rate are easy ways to bring down Postgres, but I'm personally not going to worry about exhausting connections to Postgres until I have at least a thousand of them. Everything has to be considered within the actual problem you are solving, there are definitely situations to start out with a cache.

I might be ok with this if it were built in, but pg_cron is an extension, so first off you might not even have access to it. And then you still have to monitor it.