Can you explain the principle of fault tolerance in the PostgreSQL system?

PostgreSQL's fault tolerance is ensured by several mechanisms:

• Replication — creating copies of the database on other servers (master-slave) so that data remains accessible in case of a main server failure.
• Transaction Log (WAL) — recording all changes for recovery after failures.
• Automatic Failover — when the main server crashes, the system can automatically switch to a replica.
• Backup — regularly creating copies of data for recovery.

These mechanisms together help minimize downtime and data loss.