That sounds like your archive_timeout is set to 10 seconds. (or close, as WAL segments are 16MB pre-compression). That's the maximum age of a WAL segment bef

That sounds like your archive_timeout is set to 10 seconds. (or close, as WAL segments are 16MB pre-compression). That's the maximum age of a WAL segment before rotation, and Postgres will force the log rotation even if there's no data in the WAL segment. If you're worried about keeping the last n seconds of data in replication, streaming replication is a far better tactic than log-shipping. (Though log shipping is useful for longer term storage)