Re: Questions on Upgrading PostgreSQL from 15.0 to 15.9 and Setting Up Streaming Replication

> On Nov 24, 2024, at 08:51, Subhash Udata <subhashudata@gmail.com> wrote:
> However, my concern lies in the fact that we are working with production servers, where downtime is not acceptable.

There is no way to upgrade community PostgreSQL, either to a new minor version or a new major version, with absolute zero downtime.

To do a minor version upgrade such as this, the only thing that is required is to restart the server with the new binaries.  While this does require a service interruption, it's quite short, and is not significantly longer than the interruption required to do a failover.  You can do the primary and secondary in either order, although upgrading the primary first is probably the safest route.  You don't have to switch the primary / secondary roles in this case, nor rebuild the secondary server using pg_basebackup.