What ensures the fast operation of a primary key in a database?

The quick operation of the primary key in a database is ensured by indexing. When creating a primary key, the DBMS automatically creates a unique index on this field, which allows for fast record retrieval by key value without scanning the entire table.

An index functions as a data structure (for example, a B-tree) that accelerates search, insert, and delete operations. Thanks to this, queries with conditions on the primary key are performed efficiently even on large volumes of data.