TJR Bootcamp Practice Test

An index speeds up lookups by organizing data in a way that lets the database locate rows quickly, often using a structure like a B-tree. But keeping that index up to date takes extra work. Whenever data is inserted, updated, or deleted, the index must be updated as well, which adds extra write I/O and CPU time. In addition, the index itself consumes additional storage separate from the table data. So the typical overhead of maintaining a database index is extra storage plus extra work for writes (and updates), even though reads can be much faster.