Design circuit breaker pattern when external systems fail during Salesforce callouts

• Circuit breaker states Closed Open Half-Open tracking failure rate • Open circuit fails fast with user message skip callout for cooldown period • Half-open test single request before closing circuit • Fallback: manual review queue when bureau unavailable • Platform Cache stores circuit state across transactions • Middleware circuit breaker preferred over Apex per-transaction logic • Alert when circuit opens page ops before user flood