MariaDB

Readers see a consistent snapshot without blocking writers, because an update creates a new row version rather than overwriting the old one.

The contract for which concurrency anomalies a transaction may observe, traded against how much concurrency the engine allows.

The delay between a write committing on the primary and becoming visible on a replica.

One logical write causes several physical writes - to the log, the data pages, and every affected index.

The structure that defines how data is organised in a database: tables, columns, data types, constraints, relationships, and indexes.

Organising tables so that each fact is stored once, reducing redundancy at the cost of more joins.

A data structure maintained alongside a table that makes lookups by specific columns faster, at the cost of slower writes and additional storage.

A column or set of columns that uniquely identifies every row in a table, enforced by a unique index and a NOT NULL constraint.

A constraint that links a column in one table to the primary key of another, enforcing referential integrity so that orphan rows cannot exist.

A sequence of operations that either all succeed (commit) or all fail (rollback), guaranteeing that the database moves from one consistent state to another.