Monitoring
Service Level Indicator
SLI
A Service Level Indicator (SLI) is the actual measurement of one aspect of service — usually availability, latency, error rate, or freshness. SLIs are the numbers you compare against SLOs to decide whether the service is meeting its reliability target.
In depth
Good SLIs are ratio-based: good events divided by total events. 'Percentage of homepage requests returning HTTP 2xx within 400ms' is a strong SLI. 'Average response time' is a weak one — averages hide the tail latency users actually feel.
Every SLO needs a matching SLI wired into monitoring. Lemwatch surfaces the raw SLI numbers per check (uptime %, P50/P95 latency, error rate) so teams can define SLOs against them directly.
Why it matters
Without a measured SLI, an SLO is aspirational. Wire the SLI into the alerting stack before publishing the SLO — otherwise the team can neither prove compliance nor detect breach.
Related terms
Service Level Objective
SLO means Service Level Objective — the internal reliability target a team commits to, such as 99.9% of homepa…
SLA
A service level agreement (SLA) is a contractual commitment between a provider and a customer specifying a mea…
Uptime
Uptime is the percentage of time a website or service is reachable and serving correct responses. It is the he…
Recovery Time Objective
Recovery Time Objective (RTO) is the maximum acceptable time a system can be offline after an incident before …
Recovery Point Objective
Recovery Point Objective (RPO) is the maximum amount of data loss (measured in time) a business can tolerate a…
Browse the full Lemwatch monitoring glossary (47 terms).