A practical checklist for database indexing

The version of this that works is simpler than the version most people imagine. Run through this the next time database indexing comes up.

Real-world numbers from actual visitors matter more than a score produced on a fast laptop. It rarely shows up as a line item, which is exactly why it slips.

The checklist

• The right index turns seconds into milliseconds
• Every index also slows writes, so be deliberate
• Look at the query plan instead of guessing
• Someone is named as the owner
• There is a date to review it again

Why this earns attention

The right index turns seconds into milliseconds. Small and consistent beats large and occasional here. The failure mode is not doing it wrong, it is doing it once and assuming it stays done.

What this looks like day to day

Performance work is mostly subtraction, which makes it unpopular and effective. Three things worth confirming about database indexing before you move on:

• Someone can say what the current setup is without going to look
• Look at the query plan instead of guessing — and you know whether that is true here
• There is a way to tell whether the last change to this helped

None of this needs a rewrite. Most of it is a morning's work once someone decides to do it.