We use Fleet charts via Kubernetes to host fleetdm server. We use AWS rds as the mysql database. AWS certificate is expiring, Is it ok to just replace it while Fleetdm is running? or do I have to scale down the fleetdm pod to shut it down before replacing/renewing the AWS rds cert?

I'd recommend shutting Fleet down while you're updating the certificate. You'll need to restart the server to apply the new certificate, and this way you don't need to worry about weird connection errors during the process.

Thanks a lot

Any time!