PostgreSQL 12 High Availability Cookbook - Third Edition

Being less strict

We really want to confirm whether the streaming replication works as advertised. To do this, let's shut down the standby server with this command:

sudo systemctl stop postgresql-12

Then, try to write to the primary server. This simple SQL statement should wait indefinitely:

CREATE TABLE foo ( bar INT );

If we then restart the streaming replica using the following command, we should see the transaction complete:

sudo systemctl start postgresql-12

As you might imagine, this can be problematic in true high-availability architectures that handle thousands of transactions per second. As such, we don't actually recommend that you use synchronous replication on OLTP servers. As these comprise the bulk of highly available PostgreSQL ...