SLI, SLO and SLA in Simple Words

**Chapter 4 (Service Level Objective) and my friend Rana are inspired me to write this post!.**

There’s no way to know if your system is working well, if you have no way to measure service. That’s where site reliability engineering (SRE) comes in, which implements practices to measure the services and makes the system is reliable. So, to apply these practices we need to define service-level objectives (SLOs).

SLOs

SLO is service level objective…so what?! Well, it’s numerical targets that agreed upon between stakeholders for system reliability. We know that often the dev team is under pressure to deliver the features quickly. With SLO you can know the real time of the reliability cost with new features. Hmmm…How can I define SLO for my service? The answer is by defining SLIs.

SLIs

SLI or service level indicator is quantifiable measure of service reliability. It tells us what our services are doing right now?. SLI begin by understanding of what your customers want from the system and then takes the right attention to the indicators that matter in your system. “What Do You and Your Users Care About?”
SLI should map to user expectations, such as how long it takes to return a response time to a request? It sounds like the SLO is our target for SLI, right?

SLAs

SLA is service level agreements, the promise you make about your service’s health to your customers. Okay. you’ll wonder what is the difference between an SLO and an SLA? The easy way to answer is to ask: “what happens if the SLOs aren’t met?” Therefore, if you fail to meet the SLO the SLA defines what should you do to the customer?

That’s it 😄