I'm not the OP but I'd clarify the cron check for new versions is done every minute. So when new images are pushed they're picked up quickly.

OP is not saying they push new versions at such a high frequency they need checks every one minute.

The choice of one minute vs 15 minute is implementation detail and when architected like this costs nothing.

I hope that helps. Again this is my own take.

When I push new images via CI, I want it to go in production immediately. Like Heroku/Render/Dokku