If your system relies on PostgreSQL databases and you are looking for clustering solutions for HA, we want to let you know in advance that it is a complex task, but not impossible to achieve.

PostgreSQL does not natively support any multi-master clustering solution, like MySQL or Oracle do. Nevertheless, there are many commercial and community products that offer this implementation, along with others such as replication or loading balancing for PostgreSQL.

What is High Availability?

It is the amount of time that a service is available, and is usually defined by the business.

Redundancy is the basis for high availability; in the event of an incident, we can continue to operate without problems.

Continuous Recovery

If and when an incident occurs, we have to restore a backup and then apply the wal logs; the recovery time would be very high and we would not talking about high availability.

However, if we have the backups and the logs archived in a contingency server, we can apply the logs as they arrive.

If the logs are sent and applied every 1 minute, the contingency base would be in a continuous recovery, and would have an outdated state to the production of at most 1 minute.

https://severalnines.com/database-blog/top-pg-clustering-high-availability-ha-solutions-postgresql