MariaDB Galera Cluster is a synchronous multi-master database solution that gives you true HA out of the box - every node accepts reads and writes, data is replicated synchronously across all of them, and when a node goes down it rejoins automatically when it comes back. No external orchestrator, no read-only replicas, no second job maintaining the HA layer. This is a deep dive into how it works, why I reach for it over Postgres for HA-critical systems, and how to deploy it with Docker.