sysdesign-fault-tolerance-patterns

To prevent cascading failures in distributed systems, apply the Circuit Breaker pattern with a fallback and timeout for synchronous critical dependencies. This isolates failing services, stops retry storms, and maintains system availability during outages.

The best way to handle asynchronous critical dependency failures is by combining a Dead Letter Queue (DLQ) with Exponential Backoff and Checkpointing. This ensures failed messages are safely stored for reprocessing without dropping payloads or overwhelming the system.

Use the Bulkhead pattern for fault tolerance when you need to isolate non-critical tasks, such as telemetry or logging operations. By partitioning resources, bulkheads prevent background task failures from degrading the performance of your primary synchronous services.

Configure retry policies and thresholds by encoding SLA targets, failure modes, and required metrics into your fault-tolerance configuration. This drives the selection of patterns like Exponential Backoff with jitter, ensuring time windows and retry limits are explicitly defined and versioned.

Verify fault-tolerance patterns work during an outage by implementing chaos testing and instrumentation. This validates that your Circuit Breakers, Bulkheads, and fallback mechanisms activate correctly under real failure conditions and meet your defined SLA targets.

To stop retry storms in dependent services, apply the Circuit Breaker pattern for synchronous calls and Exponential Backoff with jitter for asynchronous tasks. These canonical fault-tolerance patterns standardize resilience by controlling traffic to failing dependencies.