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SLA

/ess-el-ay/noun

Filed underBusinessInfrastructure

In brief · quick answer

A Service Level Agreement (SLA) is a contract that guarantees a minimum level of service, typically measured as uptime percentage, with financial penalties if the provider fails to meet that guarantee.

§ 1 Definition

An SLA (Service Level Agreement) is a contractual commitment between a service provider and a customer that defines the expected level of service, how it is measured, and what happens if the provider fails to deliver. In hosting and infrastructure, the most common SLA metric is uptime, expressed as a percentage (99.9%, 99.99%, 99.999%). An SLA of 99.9% allows about 8.7 hours of downtime per year. 99.99% allows about 52 minutes. The 9s matter: each additional 9 represents a tenfold reduction in allowed downtime. SLAs also cover response times for support tickets, time to fix (TTF), and credits or refunds when guarantees are missed.

§ 2 What SLAs Cover

Uptime Guarantee is the most visible metric: the percentage of time a service is available. Response Time guarantees how fast the provider will respond to support requests. Time to Fix sets limits on how long a reported issue takes to resolve. Performance Guarantees cover metrics like server response time or throughput. Financial Penalties (service credits) are the compensation you receive if the provider fails to meet any of these guarantees. Credits are usually a percentage of your monthly bill, not cash back.

§ 3 Reading SLA Fine Print

SLAs are not all created equal. Check for exclusions: scheduled maintenance, force majeure events, third-party dependencies, and customer-caused issues are often excluded from uptime calculations. Check the measurement period: a monthly 99.9% SLA is weaker than a yearly one. Check the credit structure: missing the SLA for one minute usually won't trigger credits; many providers require a sustained breach of a specific threshold. Read the SLA before you buy, not after you have a problem.

§ 4 SLA vs Actual Performance

An SLA is a floor, not a promise of normal performance. Most quality providers operate well above their SLA. For example, AWS's EC2 SLA is 99.99% per region, but actual uptime is typically much higher. The SLA defines the worst acceptable service and the compensation if that line is crossed. Do not choose a provider based solely on SLA claims; look at their actual published uptime history, third-party monitoring reports, and customer reviews.

§ 5 Note

SLAs on free or low-cost plans are often 'best effort' with no contractual guarantees. Paid plans, especially enterprise tiers, include enforceable SLAs with financial credits.

§ 6 Common questions

Q. What does 99.9% uptime actually mean?: A. 99.9% uptime allows 8.77 hours of downtime per year, or 43 minutes per month, or 10 minutes per week. Each additional 9 reduces allowed downtime by roughly 90%.
Q. Do I get money back if the SLA is breached?: A. Usually you get service credits (a percentage of your monthly bill applied to future invoices), not cash. Credits typically range from 5% to 100% depending on the severity and duration of the breach.

Key takeaways

SLA is a contractual guarantee of service quality, typically measured as uptime percentage.
99.9% allows 8.7 hours downtime per year. 99.99% allows 52 minutes. Each 9 matters.
Read the fine print: exclusions, measurement periods, and credit structures vary widely.
SLA is the floor, not the norm. Look at actual performance history, not just promises.

How Atomic Glue helps

We help clients understand SLAs when choosing hosting providers and monitor compliance on their behalf. Contact us to review your current infrastructure agreements.

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# SLA

Category: Business (also: Infrastructure)

Author: Atomic Glue Editorial Team

## Definition

An SLA (Service Level Agreement) is a contractual commitment between a service provider and a customer that defines the expected level of service, how it is measured, and what happens if the provider fails to deliver. In hosting and infrastructure, the most common SLA metric is **uptime**, expressed as a percentage (99.9%, 99.99%, 99.999%). An SLA of 99.9% allows about 8.7 hours of downtime per year. 99.99% allows about 52 minutes. The 9s matter: each additional 9 represents a tenfold reduction in allowed downtime. SLAs also cover response times for support tickets, time to fix (TTF), and credits or refunds when guarantees are missed.

## What SLAs Cover

**Uptime Guarantee** is the most visible metric: the percentage of time a service is available. **Response Time** guarantees how fast the provider will respond to support requests. **Time to Fix** sets limits on how long a reported issue takes to resolve. **Performance Guarantees** cover metrics like server response time or throughput. **Financial Penalties** (service credits) are the compensation you receive if the provider fails to meet any of these guarantees. Credits are usually a percentage of your monthly bill, not cash back.

## Reading SLA Fine Print

SLAs are not all created equal. Check for **exclusions**: scheduled maintenance, force majeure events, third-party dependencies, and customer-caused issues are often excluded from uptime calculations. Check the **measurement period**: a monthly 99.9% SLA is weaker than a yearly one. Check the **credit structure**: missing the SLA for one minute usually won't trigger credits; many providers require a sustained breach of a specific threshold. Read the SLA before you buy, not after you have a problem.

## SLA vs Actual Performance

## Note

SLAs on free or low-cost plans are often 'best effort' with no contractual guarantees. Paid plans, especially enterprise tiers, include enforceable SLAs with financial credits.

## Common questions

Q: What does 99.9% uptime actually mean?

A: 99.9% uptime allows 8.77 hours of downtime per year, or 43 minutes per month, or 10 minutes per week. Each additional 9 reduces allowed downtime by roughly 90%.

Q: Do I get money back if the SLA is breached?

A: Usually you get service credits (a percentage of your monthly bill applied to future invoices), not cash. Credits typically range from 5% to 100% depending on the severity and duration of the breach.

## Key takeaways

SLA is a contractual guarantee of service quality, typically measured as uptime percentage.
99.9% allows 8.7 hours downtime per year. 99.99% allows 52 minutes. Each 9 matters.
Read the fine print: exclusions, measurement periods, and credit structures vary widely.
SLA is the floor, not the norm. Look at actual performance history, not just promises.

## Related entries

Last updated July 2026. Permalink: atomicglue.co/glossary/sla