quality-engineering-api-performance-testing

API Performance, Load, and Recovery Testing

Priority: P1 (HIGH)

Workflow

1. Parameterize Workload: Source arrival rate vs concurrency, request mix, duration, and SLO percentiles from approved requirements/SLOs. Missing approvals block execution, not offline planning.
2. Preflight & Bound (C4): Verify explicit target authorization and synthetic isolation. Enforce distinct finite ceilings, each with its own unit — maxArrivalRateRps, maxInFlightRequests/maxConcurrency, maxPayloadBytes, duration — plus cancellation hooks and continuous stop tripwires. A rate ceiling is not a concurrency bound.
3. Establish Phase-Specific Baseline: Exclude warmup. Measure baseline throughput, success latency, error latency ($p50, p95, p99$), and baseline error budget.
4. Evaluate Overload & Degradation: Apply stepped ramp up to authorized stress cap. Distinguish expected shedding (e.g. 429/503) from unexpected system faults; abort if tripwires fire.
5. Verify Post-Overload Recovery: Drop traffic to baseline/zero. In a dedicated post-stress window, verify return to baseline latency, error budget restabilization, and resource release against approved recovery SLO.
6. Capture Evidence (C3): Emit complete C2 scenario and C3 evidence records; record unexecuted runs as BLOCKED/NOT RUN with explicit missing prerequisites.

Workload Specification (AC-11)

• Model Selection: Select open model (constant arrival rate) for uncoordinated/public traffic; closed model (virtual users) for coordinated/batch workers.
• Request Mix: Proportions of endpoints, read/write ratio, and data variance parameterized from production profiles or approved requirements.
• Warmup & Measurement: Explicit warmup window (metrics discarded from SLOs) preceding steady-state observation.
• SLO Metrics (Success & Error): Record both successful and error response latencies ($p50, p95, p99$), throughput (RPS), error budget, and resource saturation.
• Approval Gate: Operational targets must originate from approved specifications. If unapproved, mark execution BLOCKED: Missing approved SLO threshold for <metric>; continue offline planning. Numeric examples in references are synthetic fixture contracts only.