Re: compression in replication

I think this should help reduce traffic as it would decompress only when replaying.

I have not used it, but now that you asked, I will test it out.

Also, pg_basebackup supports gzip stream, and so does COPY but I do not see exclusive mention of compression support in replication slot details.

But if you try having a sidecar like envoyproxy or any tcpproxy per server, maybe communication between sidecars can be compressed but not db to sidecar.

Gzip Compressor — envoy 1.19.0-dev-069478 documentation (envoyproxy.io)  (this is not pg stuff but ... )

[pg -> sidecar -> compressed wal stream]  -> [sidecar -> decompress -> pg]

I have not tried any option, FYI.