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Is Load Behavior Under Stress Explicitly Tested?

Type: DeepDive
Category: Test
Audience: SREs, backend leads, QA engineers responsible for system resilience and scale

🔍 What This Perspective Covers

Functional tests pass.
Even performance tests might pass.
But under stress—systems don’t just slow down. They break.

⚠️ Typical Misses

  • Load tests stop at 80% CPU and never cross failure point
  • No simulation of retry storms, queue overflow, or memory saturation
  • Failure modes are untested: latency spikes, cascading failures, timeouts
  • SLOs assume averages—but user pain hides in the tail

✅ Resilience Testing Strategy

  • Define failure thresholds: latency spike? error rate? resource usage?
  • Test retry behavior, backpressure, timeouts under real contention
  • Simulate partial outages or degraded upstreams
  • Observe auto-recovery, circuit breaking, alerting response
  • Run chaos tests (within scoped blast radius) before peak seasons

🧠 Core Insight

A stable system under light load proves nothing.
Only under pressure does architecture reveal its fault lines.

❓ FAQ

  • Q: Isn’t this just performance testing?
    A: No. This is testing failure under load—not just slowness.

  • Q: What if the test breaks things?
    A: That’s the point. Better to break it intentionally.