MySQL - why not index every field?

Question

Recently I\'ve learned the wonder of indexes, and performance has improved dramatically. However, with all I\'ve learned, I can\'t seem to find the answer to this question.<

Answer 1

Keep in mind that every index must be updated any time a row is updated, inserted, or deleted. So the more indexes you have, the slower performance you'll have for write operations.

Also, every index takes up further disk space and memory space (when called), so it could potentially slow read operations as well (for large tables). Check this out