Why are database indexes important, and what are potential downsides?

Why are database indexes important, and what are potential downsides?

• A. They speed up queries but incur write overhead and storage costs.
• B. They slow down reads but speed up writes.
• C. They encrypt data to enhance security.
• D. They prevent SQL injection without any overhead.

Answer: (A)

Indexes act like speed-dials for the database, organizing data so queries can locate relevant rows without scanning the entire table. When a query filters on indexed columns or requests ordered results, the database can use the index to jump directly to the needed data, which makes reads faster. But there’s a trade-off. The index itself takes up storage because it’s a separate data structure. It also adds write overhead: every insert, update, or delete may need to update the index so it stays in sync with the table data. If a table is small or a query doesn’t use the index, the benefits can be minimal and the overhead wasted. Adding many indexes can even slow overall performance and increase maintenance work. Indexes don’t provide encryption or protect against SQL injection; those are security concerns handled by other mechanisms. So the best description is that they speed up queries but incur write overhead and storage costs.

Indexes act like speed-dials for the database, organizing data so queries can locate relevant rows without scanning the entire table. When a query filters on indexed columns or requests ordered results, the database can use the index to jump directly to the needed data, which makes reads faster.

But there’s a trade-off. The index itself takes up storage because it’s a separate data structure. It also adds write overhead: every insert, update, or delete may need to update the index so it stays in sync with the table data. If a table is small or a query doesn’t use the index, the benefits can be minimal and the overhead wasted. Adding many indexes can even slow overall performance and increase maintenance work.

Indexes don’t provide encryption or protect against SQL injection; those are security concerns handled by other mechanisms. So the best description is that they speed up queries but incur write overhead and storage costs.