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Planning & Processabbreviation · /ˌes.elˈoʊ/

SLO

In simple English

In tech companies, an SLO is a specific, quantifiable target that a team commits to meeting for a service or application. Unlike an SLA (Service Level Agreement), which is a formal contract with consequences for missing targets, an SLO is an internal goal that helps teams maintain reliability and performance standards. SLOs typically include metrics like availability (99.9% uptime), latency (response time under 200ms), or error rates (less than 0.1% errors). Teams use SLOs to balance feature development with reliability work, and to communicate service expectations to stakeholders and customers. When discussing infrastructure, product reliability, or DevOps priorities, engineers regularly reference SLOs to justify resource allocation and prioritize incident response.

Learn what Service Level Objectives are and how they are used to measure and maintain service reliability in tech companies.

At a glanceCEFR B2
Commonness4/5
Versatility4/5
FormalityCasualFormalFormal
Spoken ↔ WrittenSpokenWrittenBoth
Directness ↔ DiplomaticDirectDiplomaticNeutral
RegionUS and UK
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Say it like this

✓We need to meet our SLO for this quarter
✓This incident violated our SLO
✓What is our current SLO for API latency?

Real examples

in a standup

"We breached our SLO yesterday due to the database performance issue, so we are prioritizing optimization this sprint."

in a code review

"This change might impact our SLO, so we need to add monitoring before merging."

in a team meeting

"Our payment service SLO is 99.95% availability, which means we can afford less than 22 minutes of downtime per month."

Don't say this

Handle with care. SLO is often confused with SLA (Service Level Agreement). An SLO is a goal or target, while an SLA is a formal contract. Do not use SLO when referring to legal agreements.

✕We signed an SLO with the customer.
✓We signed an SLA with the customer, and our internal SLO is even stricter.— SLOs are internal goals, not legal agreements. SLAs are formal contracts.
✕Our SLO is 99% uptime or we lose money.
✓Our SLA is 99% uptime or we lose money. Our SLO is 99.5% uptime.— Penalties and financial consequences belong to an SLA, not an SLO.
✕We do not need an SLO for this small service.
✓We should define an SLO even for small services to clarify reliability expectations.— SLOs are useful for all services to set clear expectations and guide prioritization.

Other forms

noun

SLO

"Our authentication service has an SLO of 99.99% availability."

noun

SLOs

"We need to document all SLOs in our internal wiki."

Often used with

meet/miss an SLOUsed to describe whether a service achieves or fails to achieve its target
breach an SLOSimilar to missing an SLO; indicates failure to meet the objective
define/set an SLOUsed when establishing a new reliability target for a service
SLO violationAn incident where the service fails to meet its stated objective
SLO-drivenDescribing work or decisions that are guided by SLO targets

Similar words

Service Level ObjectiveThe full name; SLO is the abbreviation
reliability targetA less formal term for the same concept
performance goalBroader term that includes SLOs and other performance metrics

Opposites

SLA (Service Level Agreement)best effort (no specific target)

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Practice

Try it

4 quick exercises

Pick the most natural phrasing

1. Your service had unexpected downtime. A colleague asks about the impact. What do you say?

Complete the sentence

2. Before deploying this feature, we should _______ what the _______ is for page load time.

Spot the mistake

3. Which sentence uses SLO incorrectly?

Rewrite naturally

4. Rewrite this in natural tech English using SLO: 'We want our search to be really fast, like it should give answers in under half a second most of the time.'

Questions

Quick poll

Have you said "slo" in a standup this week?

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