Questions

What is a reasonable SLA?

Short answer

One that matches what the business really needs and what the system is built and paid for. Each extra nine of uptime costs more in architecture, monitoring and on-call staff, so set targets per service, and pair uptime with clear response times, maintenance windows and remedies.

Last updated 2026-10-25

What uptime percentages mean

The arithmetic, for a 30-day month (43,200 minutes):

199% allows about 7 hours 12 minutes of downtime a month.
299.5% allows about 3 hours 36 minutes.
399.9% allows about 43 minutes.
499.95% allows about 22 minutes.
599.99% allows about 4 minutes.

What else a good SLA covers

1How uptime is measured, from where, and what counts as down.
2Planned maintenance windows and how much notice is given.
3Support hours and response times by severity, and time to restore for critical incidents.
4Recovery targets for data loss and restore time after a disaster.
5Remedies, usually service credits, and when the client can terminate.
6Exclusions, such as outages of third-party services or issues caused by the client.

Check it against dependencies

Your SLA cannot be stronger than the services you depend on unless you build redundancy. If your hosting, database or payment provider commits to a lower figure, plan around it or do not promise more.

Frequently asked

Common follow-up questions.

What is the difference between an SLA and an SLO?

An SLA is the contractual promise with remedies. An SLO is the internal target the team aims for, usually a little stricter than the SLA.

Do internal tools need an SLA?

Often a lighter one: support hours and response times, without credits.

Are service credits worth much?

Usually not compared to the cost of an outage. Their real value is the incentive and the reporting that comes with them.

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