postgreSQL: streaming replication delay

From the standby DB:

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crmmbqt=# select now() - pg_last_xact_replay_timestamp() as replication_delay; ┌───────────────────────┐ │   replication_delay   │ ├───────────────────────┤ │ 1 day 05:45:26.277667 │ └───────────────────────┘

or get more details with

1	crmmbqt=# pg_last_xlog_receive_location(), pg_last_xlog_replay_location(), pg_last_xact_replay_timestamp(), case when pg_last_xlog_receive_location() = pg_last_xlog_replay_location() then 0 else extract(epoch from now() - pg_last_xact_replay_timestamp()) end as replication_delay;