What is the difference between MyISAM and InnoDB?

MySQL supports multiple storage engines. InnoDB and MyISAM were historically the two main choices. InnoDB (default since MySQL 5.5): supports ACID transactions (COMMIT/ROLLBACK); row-level locking (fine-grained, high concurrency); foreign key constraints and referential integrity; crash recovery via redo logs; MVCC for non-locking reads; better performance for mixed read/write workloads. MyISAM (legacy): no transaction support; table-level locking (one write locks the whole table — poor concurrency); no foreign keys; faster for read-heavy workloads without writes; supports FULLTEXT indexing (InnoDB added FULLTEXT in MySQL 5.6+); table data is stored more simply (can be faster to count rows as it stores the count). Verdict: Always use InnoDB for new applications. The only remaining use cases for MyISAM are legacy systems or extremely specific read-only analytical workloads. MySQL 8.0 still supports MyISAM but it is essentially deprecated for new development. For analytics, consider columnar engines like ClickHouse or MySQL's NDB Cluster for specialized workloads.