Distributed-systems

How the circuit breaker pattern protects microservices from cascading failures: states, slow-call thresholds, fallbacks, retry interaction, and metrics.

Why adding more service instances can leave throughput flat when the bottleneck is a shared database, lock, connection pool, queue, or dependency.

Why request timeouts limit waiting but cannot stop cascading failures without admission control, bounded queues, backpressure, and load shedding.

Why read replicas often fail to reduce primary database load when reads are coupled to writes, replica lag triggers fallback, and query cost is misread.

Why retry logic can amplify degraded systems, how retry budgets and jitter reduce retry storms, and what to check before retrying production requests.