pg_standby is a contrib module providing a utility program supporting the creation of a warm standby server.
pg_standby was introduced in PostgreSQL 8.3, and supports PostgreSQL 8.2 and later. It is likely to be removed in PostgreSQL 14 (pgsql-hackers thread: [PATCH] remove pg_archivecleanup and pg_standby).
With the exception of bugfixes and minor code changes,
pg_standby has remained unchanged since PostgreSQL 8.4.