Circuit Breakers Under Stress: Anatomy of a Payment Cascade

Short summary

A 10x traffic spike pushed payment system circuit breakers into cascade mode when Stripe latency hit 14s. The breaker design itself was sound, but the thread pool configuration lacked dependency isolation, allowing a single slow downstream to saturate resources. Solutions implemented: tighter failure thresholds (30%), slow-call detection, per-dependency bulkheads, and async payment processing via outbox pattern.

• •Configuration allowed 50% failure threshold over 100 calls — too lenient under 10x load
• •Single thread pool created bottleneck when Stripe response times increased to 14s
• •Fixes: threshold reduction to 30%, slow-call detection, per-dependency bulkheads, async payment architecture

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