Service level objective (SLO)
An SLO sets a target for a defined service-quality measure over a stated period.
A service level objective, or SLO, is a target value or range for a defined aspect of service quality. A service level indicator, SLI, measures it. The measurement rule and period are part of the target.
For a fictional search, the SLO is: at least 99.5% of valid requests in a calendar month receive a correct answer within 2 seconds. If only 990 of 1,000 requests qualify, the measured SLI is 99%; the example target is missed. These values are not an ASES commitment.
“Fast and available” lacks a sufficiently testable measurement definition. A useful SLO informs operational decisions, such as prioritising a recurring failure. The measured result remains separate from the target.
Sources
Related terms
- Service level indicator (SLI)An SLI is a clearly defined measure of an aspect of service quality that matters to users.
- Audit logAn audit log makes important application events traceable. Actor, action, affected object and outcome need to be readable together.
- MonitoringMonitoring continuously collects and evaluates selected system states and functions. What it tells you depends on what is actually observed.
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