I used these three terms interchangeably, and many people around me did the same. One day, I decided to sit down and properly understand the difference between them. If you have also thought they were basically the same thing, welcome to my first article.

When building reliable systems, engineers often hear terms like SLI, SLO, and SLA used interchangeably. They are related, but each serves a very different purpose.

A simple way to think about them:

SLI = What is happening

SLO = What we want