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To ensure high fault tolerance in PostgreSQL, the following methods are used:

• Replication: creating copies of the database on other servers (master-slave or streaming replication) so that in case of failure, a replica can take over.
• Automatic failover: using tools (e.g., Patroni, repmgr) to automatically switch to a replica upon master failure.
• Backups: regular backups (pg_dump, pg_basebackup) for data recovery.
• Monitoring and alerting: tracking server and replication status for quick response.
• Clustering and distributed systems: e.g., Citus for scaling and fault tolerance.

Example: setting up streaming replication provides a hot standby that is synchronized with the primary server almost in real-time.