Doesn't that run into their rate limits if you generate a certificate every few minutes all the time? Or at least might be a burden, even if it didn't hit an absolute limit. (I'm assuming you're not the only person in the world doing this, so I mostly mean the collective effect this sort of usage pattern has)

Sorry, I should have clarified. You can't do certificates that fast on Let's Encrypt no. I meant running a custom CA inside/alongside Kubernetes, and using that to issue 20-minute validity certs to pods.