Hijrah Backend (5): The Query That Said 'Use My Index'

Thu, 10 Sep 2026 15:30:00 +0700

In episode two, the query was innocent, 78 milliseconds in the CLI while the endpoint burned 15 seconds. This episode is the mirror image: this time the query was truly guilty. But not because it was complex or ugly, it was guilty because one small function wrapper made it ignore an index built specifically for it hehe~

A Perfectly Designed Index (Times Three) #

The victim: an endpoint counting alerts per device. Its alert table holds tens of millions of rows,¹ and on top of it sits a composite index: (date, device, alert type). Read the endpoint’s needs, “count alerts per device per type, within a date range”, and that index looks like it was built for exactly this query. Someone in the past understood the problem perfectly.

Sql on Blogfolio Najib

Hijrah Backend (5): The Query That Said 'Use My Index'

A Perfectly Designed Index (Times Three) #