PostgreSQL 9.2 high replication lag

Hello all,

I have a cluster of PostgreSQL 9.2 servers (yes, I know... we're working on a migration to PG 13) that has one master and one slave.

I know that the streaming replication is expected to have delays, but this is getting worse and worse everyday. You can see the replication gap is reaching >10 minutes quite often.

The servers are hosted in AWS as EC2 instances and they're both in different AZs. I also know that the streaming replication was first introduced in PG 9.0, so we're using a very old version of it.. I'm sure it has improved over the years...

What can I look for to make this lag not so high? Is there anything I could change in my postgresql.conf files? Any tips?

Thanks!