Backend concept

Circuit Breakers

Open, half-open, and closed states; timeouts, fallback behavior, failure classification, and dependency isolation.

Why this matters

Circuit breakers prevent one failing dependency from spreading latency and resource exhaustion across the system.

Decide when to open, probe, close, retry, or serve a fallback.

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No local review items for this concept yet.

Choose when to open, half-open, and close a circuit breaker.
Design fallbacks that preserve business correctness.
Combine timeouts, bounded retries, jitter, and bulkheads to reduce blast radius.
Compare routing strategies under changing server capacity.
Understand overload, latency, and health-aware routing.
Connect horizontal scaling to practical traffic distribution.

Using very long timeouts that hold threads and amplify outages.
Counting expected 4xx validation errors as dependency-health failures.
Retrying without jitter, budgets, or idempotency.
Serving stale data for correctness-critical decisions such as inventory or payments.
Treating all servers as equal when they have different capacity.
Ignoring server health during traffic spikes.

Start with the first game, then use local review history to revisit missed decisions.

Reliability Intermediate

Diagnose dependency failures and choose circuit breaker, timeout, fallback, retry, half-open, and bulkhead strategies that reduce blast radius.

Time: 6-9 minutes
Concept: Circuit breakers, timeouts, retries, fallbacks, and dependency isolation

Scaling Intermediate

Route simulated traffic across backend servers using round robin, weighted round robin, least connections, and random strategies.

Reliability Intermediate

Triage production incidents by choosing useful metrics, logs, traces, queue signals, database evidence, request ids, and alerting strategies.

Time: 6-9 minutes
Concept: Production observability, incident triage, metrics, logs, traces, and alerts