Circuit Breakers
Failing fast on a broken dependency, and what you fail fast to.
6 to work through
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intermediate Multiple choice
A team proposes circuit breakers on every downstream call. What would you add, and why is the breaker not the most important control?
2 min answer -
intermediate
Your circuit breaker opens during normal traffic spikes, causing outages it was meant to prevent. How do you configure it correctly?
2 min answer -
advanced
A card-processing platform's downstream authorisation network is slow but not failing - responses arrive, just far too late. Why does a standard error-rate circuit breaker not help, and what does?
2 min answer -
advanced
A grocery platform's retailer inventory API is slow but not failing - responses take 6 seconds instead of 200 ms, and mostly succeed. Should the circuit breaker open? Analyse the trade-off.
2 min answer -
advanced
After adding circuit breakers, a partial outage now lasts three times longer than it used to. What is likely happening?
1 min answer -
advanced
You maintain circuit breakers across 200 services. Configuration drift means half are misconfigured. What do you do?
2 min answer
5 terms in this topic
Circuit Breakers in Practice
What a breaker is actually for, the configuration that stops it causing the outage it prevents, and why Netflix moved away from static thresholds.
conceptFailure Threshold
The condition that trips a circuit breaker — best expressed as a failure rate over a rolling window with a minimum request volume, not as a consecuti…
patternFallback Strategy
What a caller does instead when a circuit breaker is open — the part of the pattern that determines whether failing fast helps anyone.
conceptHalf-Open State
The circuit breaker state that allows a limited number of trial requests through to test whether a failed dependency has recovered.
case-studyNetflix: From Hystrix to Adaptive Concurrency Limits
Netflix's widely-copied circuit breaker library was retired in favour of limits that derive themselves from observed latency, because static threshol…
Neighbouring topics
Distributed Systems
General material on partial failure, coordination and distributed reasoning.
CAP & PACELC
What you must give up during a partition, and the latency choice the rest of the time.
Consistency Models
Linearizable, sequential, causal, eventual, and the session guarantees between them.
Idempotency
Making an operation safe to repeat, because a client that times out cannot know.
Retries & Backoff
Exponential backoff, jitter, retry budgets, and how retries become the outage.
Timeouts & Deadlines
Per-hop timeouts that do not compose, and the deadline budget that replaces them.
Backpressure & Flow Control
Telling callers to slow down instead of buffering into congestion collapse.
Load Shedding
Rejecting some work deliberately so the rest can be served correctly.
Bulkheads & Isolation
Partitioning resources so one dependency cannot starve the others.
Leader Election
Agreeing who is in charge, and fencing the one who no longer is.
Consensus Protocols
Raft, Paxos and quorums — what they guarantee and what they cost.
Distributed Locking
Mutual exclusion across machines, and why it is harder than it looks.
Distributed Transactions
Two-phase commit, its blocking failure mode, and when it is still reasonable.
Sagas & Compensation
Replacing atomicity with semantic undo, and ordering the irreversible steps last.
Service Discovery
Finding a healthy address for something whose instances are ephemeral.
Messaging & Queues
Decoupling producer from consumer, and the semantics that come with it.
Event Streaming
Retained ordered logs, consumer offsets, partitions and replay.
Clocks & Ordering
Why wall clocks lie, and how logical clocks and versions restore order.
Failure Modes
Slow rather than down, partial, grey, and failing while reporting success.