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SLA Model

APIContext lets you define Service Level Objectives (SLOs) for your monitors and projects. These SLOs are the thresholds that determine what the CASC Quality Score measures against.

Definitions​

TermMeaning
SLOService Level Objective — a target you set (e.g. "99.9% uptime", "p95 latency < 500 ms")
SLAService Level Agreement — a contract with a customer that formalises one or more SLOs
SLIService Level Indicator — the actual measured value the SLO is assessed against

In APIContext, every monitor run produces SLIs. The SLO defines the pass threshold. The CASC Score reflects whether recent SLIs are meeting the SLO.

CASC score as an SLO health indicator​

The CASC Quality Score (0–9.99) is APIContext's composite representation of SLO health:

  • A score ≥ 8.00 indicates the SLO is being met
  • A score < 8.00 is the default alert threshold

The 8.00 threshold is configurable per project. Organisations with stricter SLAs might set a minimum of 9.00; teams with relaxed SLAs might accept 7.00.

Types of SLO in APIContext​

Availability SLO​

Percentage of monitor runs that pass within a given time window:

  • Target: e.g. 99.9% uptime over 30 days
  • Measured by: pass/fail rate from your scheduled monitors

Latency SLO​

Maximum acceptable response time at a given percentile:

  • Target: e.g. p95 < 500 ms, p99 < 1000 ms
  • Measured by: latency data from each monitor run

Conformance SLO​

Percentage of runs that pass conformance checks:

  • Target: e.g. 100% schema conformance
  • Measured by: conformance results from each monitor run

Performance Change Thresholds​

APIContext supports alerting on relative degradation in addition to absolute SLO breaches. The Performance Change Thresholds feature fires a webhook or alert when:

  • Latency increases by more than N% compared to a rolling baseline
  • Pass rate drops by more than N percentage points compared to historical average

This catches gradual degradation that stays technically within the SLO but represents a meaningful trend.

Setting up SLOs​

See SLO/SLA management guide for step-by-step instructions.

See also​