Service Level Agreement (SLA)

What is Service Level Agreement (SLA)?

An SLA is a contract that explicitly defines the service quality a service provider promises to customers and their responsibility for achieving it. It defines measurable metrics such as uptime, response time, and resolution time, and also specifies penalties if these are not achieved.

In a nutshell: A contract where service providers and users promise “We will provide this service at this level.”

Key points:

• What it does: Establishes service quality standards and monitors and reports on achievement
• Why it’s needed: Clarifies customer expectations, builds trust, and defines responsibilities for both parties
• Who uses it: Cloud providers, ISPs, outsourcing companies, all service companies

Why it matters

Without an SLA, expectations between customers and providers remain misaligned. Customers might expect “always available” while providers think “weekly maintenance is enough.” This misalignment leads to disputes.

By clarifying SLAs, both parties can build relationships on the same page. Moreover, defining service credits (refunds) for non-achievement raises provider incentives.

Calculation method

The most common SLA metric is “uptime.” The calculation method is as follows:

Uptime (%) = (Total period - Downtime) ÷ Total period × 100

Example: 2 hours downtime in one month (720 hours) = (720-2)÷720×100 = 99.72%

Response time is measured by “time to first contact,” and resolution time is measured by “time to complete problem resolution.”

Benchmarks

Cloud providers typically offer 99.9-99.99%, with 99.99% and above requiring consultation.

Real-world use cases

Cloud hosting Guarantees 99.99% uptime and refunds 10% of usage fees if this standard isn’t met.

Telephone line service Promises 30-second average response time, with credits if exceeded.

Customer support Priority 1 issues are handled within 1 hour, resolved within 8 hours, with refunds for non-achievement.

Benefits and considerations

Benefits: Aligned expectations, accountability, and continuous improvement are promoted, reducing disputes.

Considerations: Setting unrealistic targets means they can’t be achieved and refunds continue. Additionally, disagreements about measurement methods can arise.

Related terms

• Uptime — the most common SLA metric
• Response Time — important metric for measuring service quality
• Customer Experience (CX) — quality promised by SLA
• Quality Management — mechanisms to achieve SLA
• Service Metrics — targets for SLA measurement

Frequently asked questions

Q: Is refund always provided for SLA violations? A: Natural disasters and customer-side issues are often excluded. Check the contract details.

Q: Is there a noticeable difference between 99.9% and 99.99% uptime? A: Yes. 99.9% means about one day of downtime yearly, while 99.99% means less than an hour. Business impact differs significantly.