MySQL

The veteran relational database behind a huge share of the web: WordPress, Shopify and PlanetScale territory.

MySQL is the relational database that powered the first web: full SQL, ACID transactions, battle-tested replication, and the LAMP stack's storage layer. It remains the default at hosting providers, in content platforms like WordPress, and inside companies whose tooling grew around it.

Why founders use it: ubiquity. Every host, every ORM, every backup tool speaks MySQL, and managed versions exist at every cloud. For PHP-era products and WordPress-adjacent tooling, it is often already there, which beats introducing a second engine. InnoDB delivers proper transactions, and the JSON column support covers semi-structured data without abandoning SQL.

A realistic setup: a managed instance, migrations from the ORM, read replicas when reporting queries start to interfere, and routine backups verified by an actual restore. Schema changes on large tables want planning; online DDL and pt-osc are the tools of the trade.

Trade-offs: the advanced SQL surface, window functions, CTEs, extension ecosystem, is narrower than Postgres's, and the ecosystem's center of gravity has shifted. Compare with Postgres for new products and with MariaDB for the community fork tradition.