Infrastructure & Platforms · core
Reliability & Fault Tolerance
SLOs, error budgets, redundancy, graceful degradation, overload control, and failure-domain design.
Mental model
Reliability is a measurable product property. Define an SLO, budget failure, isolate fault domains, shed optional work, and test recovery before incidents. Scope: this card owns the target-setting layer — deciding what 'reliable enough' means and budgeting for it with SLOs, error budgets and fault domains. Staying CORRECT while a request is failing is `distributed-failure-recovery`; the concrete queue-retry mechanism is `retries-dlq`.
How to study Reliability & Fault Tolerance
Begin by restating the mental model in your own words, then connect it to a concrete system you have built or operated. Name the mechanism, the constraint it addresses, and the trade-off it introduces. Use Google Site Reliability Engineering to check details, but close the source before writing your explanation. Retrieval is the learning step; rereading is only preparation.
Next, compare Reliability & Fault Tolerance with Background Jobs, Retries & DLQ. Ask what changes in correctness, latency, resource use, operability, and failure recovery. Complete Design exercise: Reliability & Fault Tolerance and preserve the command, input, output, and one failed attempt as evidence. Finish by explaining the idea without jargon to someone who has not studied the track.
Proof of understanding
- Explain the mechanism from first principles and identify the state it reads or changes.
- Give one situation where the concept is the right choice and one where it is not.
- Predict a realistic failure mode before running the drill, then compare the prediction with evidence.
- Connect the result to a roadmap or build artifact instead of treating the concept as isolated trivia.
Learn from primary sources
Practice and explain it back
Design exercise: Reliability & Fault Tolerance
SLOs, error budgets, redundancy, graceful degradation, overload control, and failure-domain design. Implement designOutline() returning non-empty values for: slo, failureDomain, degradationMode. Each value must name a concrete mechanism or decision.
Expected evidence: A design outline with slo, failureDomain, degradationMode plus an explicit failure mode or trade-off.
Open the interactive drill →Review prompts
- What is an error budget for, and what should happen when it is exhausted?
Build evidence
Synthesize: Infrastructure & Platforms
Design and operate a reproducible, observable, fault-tolerant platform for untrusted workloads. Produce one working system, benchmark, or evidence-backed design that integrates the path.
- Implements or precisely models the core mechanisms from all three milestones
- Includes at least one injected failure or adversarial case and demonstrates recovery
- Reports quality, latency, resource, reliability, or usability measurements relevant to the domain
- Ships a concise architecture note explaining decisions, trade-offs, and remaining risks