Speed Is A Feature

If your system feels slow, users don’t file bug reports; they just stop using it. Indexes and query optimization are the secret sauce behind “feels instant.” They turn “go find the needle in the haystack” into “go to aisle 5, top shelf, third bin.”

We’re designing for speed, reliability, and stability. In practice, that means building data access paths that are predictable and cheap. In interview speak: can you make the database do less work, consistently?

Mental model: indexes reduce “how much data the database must touch” to answer your question.