InnoDB: the default engine with ACID transactions

InnoDB is a general-purpose storage engine balancing high reliability and high performance, and in MySQL 8.4 it is the default storage engine: a CREATE TABLE statement without an ENGINE clause creates an InnoDB table unless a different default is configured. Its DML operations follow the ACID model, with transactions featuring commit, rollback, and crash-recovery capabilities to protect user data. Row-level locking and Oracle-style consistent reads increase multi-user concurrency and performance, and InnoDB supports MVCC with row locking granularity and a 64TB storage limit. Every InnoDB table has a primary key index called the clustered index that arranges data on disk to minimize I/O for primary key lookups, so choose primary keys with lookups in mind. InnoDB also supports FOREIGN KEY constraints, checking inserts, updates, and deletes so they cannot produce inconsistencies across related tables. Keeping tables on InnoDB unless a workload has a documented need for another engine is Koskamo editorial guidance. Scope: MySQL 8.4. Reviewed October 4, 2026.