Five mistakes teams make with database indexing

Teams tend to reach for this after something has already gone wrong. These are the ones we run into repeatedly when we audit database indexing.

Performance work is mostly subtraction, which makes it unpopular and effective. Budget a little time for it every quarter and it never becomes a project of its own.

The mistakes we see most

• Treating it as a launch task rather than an ongoing one
• Assuming someone else already owns it
• The right index turns seconds into milliseconds
• Every index also slows writes, so be deliberate
• Never checking whether the fix actually worked

Look at the query plan instead of guessing. The cost of getting this wrong is rarely visible on the day it happens. If it only works because one person remembers to do something, it does not work yet.

What to do next

In practice

Real-world numbers from actual visitors matter more than a score produced on a fast laptop. 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

If any of that sounds like a description of your current setup, it is fixable.