What is an SLA?

Service Level Agreements explained: uptime guarantees, what the numbers mean, and why they matter for your business.

An SLA (Service Level Agreement) is a contract between a service provider and customer that defines the expected level of service. For cloud services and APIs, this typically means uptime guarantees—how much the service promises to be available.

What's in an SLA?

A typical uptime SLA includes:

  • Uptime guarantee – The percentage of time the service will be available (e.g., 99.9%)
  • How uptime is measured – Usually monthly, with exclusions for scheduled maintenance
  • Service credits – Compensation (usually billing credits) if the SLA is breached
  • Exclusions – What doesn't count toward downtime (maintenance windows, customer-caused issues, etc.)
  • How to claim credits – The process for requesting compensation after an outage

What do uptime percentages mean?

Small differences in uptime percentages translate to big differences in allowed downtime:

Uptime Downtime/Year Downtime/Month Common name
99% 3.65 days 7.3 hours "Two nines"
99.9% 8.76 hours 43.8 minutes "Three nines"
99.95% 4.38 hours 21.9 minutes —
99.99% 52.6 minutes 4.4 minutes "Four nines"
99.999% 5.26 minutes 26.3 seconds "Five nines"

Use our uptime calculator to see exactly what any SLA percentage means in real time.

Real-world SLA examples

Cloud providers

  • AWS – Most services offer 99.99% SLA, with service credits ranging from 10% to 100% based on uptime achieved
  • Google Cloud – Generally 99.95% to 99.99% depending on the service
  • Azure – 99.95% to 99.99% for most services

SaaS products

  • Slack – 99.99% for paid plans
  • Salesforce – 99.9% or higher depending on edition
  • Stripe – 99.99% for core APIs

Why SLAs matter

For businesses using services

SLAs set expectations. If a critical vendor goes down, you know what compensation to expect and can plan accordingly. They're also useful for evaluating vendors—a service with no SLA or a weak SLA may not be reliable enough for production use.

For businesses providing services

Offering an SLA builds customer trust. It shows you're confident in your reliability and willing to stand behind it. But be careful—promising too much can be expensive if you can't deliver.

What SLAs don't cover

Most SLAs have exclusions. Common ones include:

  • Scheduled maintenance – Planned downtime usually doesn't count
  • Force majeure – Natural disasters, war, etc.
  • Customer-caused issues – Problems from your code or configuration
  • Third-party failures – Upstream providers, DNS, etc.
  • Beta or preview features – Often explicitly excluded

Pro tip: Read the fine print

SLA credits are usually applied to future bills, not paid out in cash. They're often capped at a percentage of your monthly spend. And you typically have to request them within a specific timeframe after an outage. Always read the full SLA terms.

FAQ

An SLA (Service Level Agreement) is a commitment between a service provider and customer that defines expected service levels, including uptime guarantees and compensation for failures.

99.9% uptime means the service can be down for up to 8.76 hours per year, or about 43 minutes per month.

Most SLAs include service credits when uptime falls below the guarantee. The exact compensation depends on contract terms.

Uptime = (Total time - Downtime) / Total time × 100. Most providers measure monthly, excluding scheduled maintenance.

Learn more

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