Indicator, objective, agreement

Three terms get used interchangeably, and they mean different things. Separating them isn't pedantry: each one has a different author, a different consequence and a different reason to exist.

The indicator

A service level indicator is a measurement: a number, taken from the system, that describes something a user experiences.

"The proportion of requests that returned a success status within 500 milliseconds."

It has no target attached. It's a number that can be observed. The senior course "Operations: system health" showed where this application's raw material for one would come from: its request logs and Cloudflare's view of traffic and errors.

The objective

A service level objective is a target for that indicator, and you choose it.

"That proportion should be at least 99.5%, measured over 30 days."

It's internal. Missing it has no external consequence. What it gives you is a decision, made in advance, about what you'll do when you miss it.

The agreement

A service level agreement is a promise to someone else, usually with money attached.

"If availability falls below 99.5% in a month, you get a refund."

It's a commercial instrument. It should always be looser than your objective, so that you find out you're in trouble before your customers get to tell you.

flowchart TB
  I["indicator: a measurement, no target"] --> O["objective: a target you chose, internal"]
  O --> A["agreement: a promise to others, with consequences"]
  O --> G["set the objective tighter than any agreement"]
  G --> W["so you learn about trouble before customers do"]

Why the distinction earns its keep

Teams that skip the indicator write objectives about things they can't measure. "The site should be fast" isn't an objective, because nothing can be compared against it.

Teams that conflate the objective and the agreement set their internal target at the level they promised, which leaves no margin. The first time they miss internally, they've already missed externally.

For an application at an early stage, the useful question is which of the three to write down first. Lesson 6 answers it, and the answer is the leftmost one.

Key takeaways

• An indicator is a measurement with no target attached.
• An objective is a target for that indicator, chosen internally, with no external consequence.
• An agreement is a promise to someone else, usually commercial.
• The objective should always be tighter than the agreement, so trouble shows up internally first.
• Without an indicator, an objective is about something nothing can be compared against.