Site Reliability Engineering Flashcards

What is a circuit breaker pattern?

Answer: A design pattern that stops sending requests to a failing service to allow it to recover, instead of overwhelming it

The circuit breaker opens when a service exceeds a failure threshold, redirecting or failing fast for requests instead of waiting for timeouts, protecting the caller and giving the failing service recovery time.

What is 'observability-driven development'?

Answer: Building systems with instrumentation and telemetry from the start so they are intrinsically observable

Observability-driven development treats telemetry as a first-class concern, ensuring every feature ships with the metrics, logs, and traces needed to understand its behavior in production.

What is 'progressive delivery'?

Answer: Releasing features incrementally to subsets of users using feature flags, canary releases, or A/B testing

Progressive delivery decouples deployment from release, using techniques like feature flags and canary releases to control who sees new features and roll back instantly if needed.

What is a load balancer health check?

Answer: A periodic test sent to backend instances to determine if they are healthy and should receive traffic

Load balancers use health checks (HTTP, TCP, or custom probes) to automatically remove unhealthy instances from the rotation and restore them once they pass checks again.

What is backpressure in distributed systems?

Answer: A mechanism where a downstream service signals upstream services to slow down when it's overwhelmed

Backpressure prevents cascading overload by letting overwhelmed services reject or slow requests, signaling upstream callers to reduce their send rate.

What is a 'golden signal' in SRE monitoring?

Answer: One of four key metrics: latency, traffic, errors, and saturation

The four golden signals (from Google's SRE book) — latency, traffic, errors, and saturation — are the most critical metrics to monitor for any user-facing service.