Terminology for PostgreSQL®

Primary node

The PostgreSQL® primary node is the main server node that processes SQL queries, makes the necessary changes to the database files on the disk, and returns the results to the client application.

Standby node

PostgreSQL standby nodes (also called replicas) replicate the changes from the primary node and try to maintain an up-to-date copy of the same database files that exists on the primary node.

Write-Ahead Log (WAL)

The WAL is a log file storing all the database transactions in a sequential manner.

pglookout

pglookout is a PostgreSQL replication monitoring and failover daemon.

PGHoard

PGHoard is a PostgreSQL backup daemon and restore tooling that stores backup data in cloud object stores