I receive such error sometimes on heroku:

at=error code=H15 desc="Idle connection" method=GET

In heroku docs says about H15 error:

The dyno did not send a full response and was terminated due to 55 seconds of inactivity.

It means heroku didn't get response from prisma due to request limit, right?

no, the dyno will turn into idle (sleep mode) due to inactivity. source: https://devcenter.heroku.com/articles/free-dyno-hours#dyno-sleeping

@catalinmiron hm, i don't think that's the issue. I use uptimerobot.com right now for making request to my server every 25 minutes (app goes to sleep after 30 minutes of inactivity), so it shouldn't go to sleep