postgresql replication replay lag

[Kenny Bachman <kenny.bachman17@xxxxxxxxx>]

Hello PG Team,

I have a 3-nodes Patroni cluster with PG 12.9. There is a replay lag on the third node. I don't understand why there is lag. The replication view output is below :

Extra info: There is no long-running query on the third node.

Where can I check to detect what's causing this?

Thank you,

Best,

Kenny

-[ RECORD 1 ]----+------------------------------
pid              | 1442401
usesysid         | 15302
usename          | replicator
application_name | henb
client_addr      | 10.109.15.94
client_hostname  | henb.acc
client_port      | 43286
backend_start    | 2021-11-13 15:16:43.462115
backend_xmin     |
state            | streaming
sent_lsn         | 8E66/4FC9F618
write_lsn        | 8E66/4FC9F618
flush_lsn        | 8E66/4FC9F618
replay_lsn       | 8E66/4F58F000
write_lag        | 00:00:00.000653
flush_lag        | 00:00:00.00126
replay_lag       | 00:00:05.463059
sync_priority    | 0
sync_state       | async
reply_time       | 2021-12-27 17:02:56.750262+03
-[ RECORD 2 ]----+------------------------------
pid              | 1390172
usesysid         | 15302
usename          | replicator
application_name | henc
client_addr      | 10.109.15.95
client_hostname  | henc.acc
client_port      | 47982
backend_start    | 2021-11-13 15:19:42.065277
backend_xmin     |
state            | streaming
sent_lsn         | 8E66/4FC9F618
write_lsn        | 8E66/4FC9F618
flush_lsn        | 8E66/4FC9F618
replay_lsn       | 8E63/6E340B20
write_lag        | 00:00:00.010311
flush_lag        | 00:00:00.01101
replay_lag       | 02:00:15.147839
sync_priority    | 0
sync_state       | async
reply_time       | 2021-12-27 17:02:56.7555