MariaDB

MariaDB was created in 2009 by the original developers of MySQL as a community-driven fork following Oracle's acquisition of Sun Microsystems. It remains API- and SQL-compatible with MySQL, making it a drop-in replacement in most stacks, while diverging meaningfully in its internals — particularly the query optimizer, thread pool, and storage engine lineup.

The Community Server is released entirely under the GPL with no contributor licence agreement required, making it a cleaner open-source commitment than MySQL. The MariaDB Foundation, a nonprofit, stewards the project and its roadmap independent of any commercial vendor.

Key technical differentiators over MySQL include: a thread pool available in the community edition (MySQL restricts this to Enterprise), the Aria storage engine for crash-safe temporary tables, ColumnStore for analytical workloads, Galera Cluster for synchronous multi-primary replication, and a more aggressive optimizer development cycle with features like Rowid Filtering and improved statistics.

MariaDB is the default MySQL replacement in many Linux distributions (Debian, Ubuntu, RHEL). It is natively supported by WordPress, Laravel, Django, and Rails, and is available as a managed service via AWS RDS for MariaDB, Google Cloud SQL, Azure Database for MariaDB, and Aiven.