NOTE
MySQL Storage Engines
The storage-engine abstraction and why InnoDB is the normal transactional choice.
This is a historical learning note and may contain outdated or incomplete understanding.
MySQL separates the SQL/server layer from pluggable storage engines. The engine owns physical row/index storage and much of transaction, locking, and recovery behavior.
InnoDB is the standard choice for transactional applications because it provides MVCC, crash recovery, row/range locking, foreign keys, and durable transactions. Engine comparisons should be based on required semantics and supported versions rather than old feature matrices.