Service Level Agreement (SLA)

99.9% (three nines) allows about 8.7 hours of downtime per year and is a common commercial standard for SaaS. 99.95% allows about 4.4 hours. 99.99% (four nines) allows about 52 minutes and requires highly redundant infrastructure.

A service credit is a discount or rebate on future fees, applied when the provider misses an SLA metric. It is not a cash payment. Credits are typically calculated as a percentage of the monthly fee proportional to the severity and duration of the breach.

Only if the SLA or MSA allows it. A well-drafted SLA specifies that service credits are the sole remedy for SLA breaches (unless there is gross negligence or wilful default), protecting the provider from unlimited liability.

Scheduled maintenance windows, force majeure events, incidents caused by the client's configuration or third-party integrations, and third-party infrastructure failures are typically excluded. These carve-outs must be explicit.

Per customer. Each customer's SLA entitlement is measured for their specific account. A global outage that affects all customers triggers the SLA for each affected account.

Yes — enterprise tiers commonly carry higher SLA commitments and faster response times. A tiered SLA is a legitimate commercial and technical differentiation.