Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
60 results for “Resilience Testing”
Chaos Engineering
Deliberately injecting failure into a system to discover, before an incident does, which of your resilience assumptions are false.
Game Day
A scheduled exercise in which a failure is deliberately introduced and the team responds as though it were real, to test the system and the response together.
Contract Testing
Verifying that a provider satisfies the expectations each of its consumers actually relies on, without running all the services together.
Load Testing
Driving a system with realistic traffic at a target volume to verify it meets its performance targets before real users do.
Availability Calculation
Deriving a system's availability from its components, remembering that dependencies in series multiply.
Availability Zone
One or more physically separate data centres inside a cloud region, with independent power, cooling and network, connected by low-latency links.
Blameless Postmortem
An incident review that seeks the systemic conditions that made a failure possible, explicitly excluding individual fault.
Blast Radius
The set of things that break, or become reachable, when one component fails or is compromised.
Blast Radius Reduction
The set of deliberate partitions — accounts, regions, zones, cells, tenants, deployment stages — that bound how far any single failure or compromise can reach.
Booking.com's Experimentation Platform
Booking.com runs over a thousand concurrent experiments and treats the ability to test any change safely as a platform capability rather than a product feature.
Bulkhead
Partitioning resources so that exhaustion caused by one dependency or tenant cannot starve the others.
Capacity Planning
Deciding in advance how much capacity will be needed, given growth, seasonality and failure scenarios, and ensuring it can be there in time.
Circuit Breaker
A proxy that stops calling a failing dependency after a failure threshold, failing fast instead, and periodically tests whether it has recovered.
Control Plane and Data Plane
The separation between the machinery that makes changes to a system and the machinery that serves its traffic.
Disaster Recovery
The plan and capability for restoring service after an event that takes out a whole site, region or system.
Error Budget
The amount of unreliability an SLO permits, treated as a resource that feature velocity spends.
Exponential Backoff
Increasing the wait between retries geometrically, with random jitter, so that failures do not synchronise into a stampede.
Failure Thinking
Making "what happens when this fails?" a standing question applied to every component and every dependency in a design.
Fallback Strategy
What a caller does instead when a circuit breaker is open — the part of the pattern that determines whether failing fast helps anyone.
Fault Tolerance
Continuing to operate correctly despite the failure of some components, by design rather than by luck.
Fitness Function
An automated check that an architectural characteristic still holds, run continuously rather than reviewed occasionally.
Graceful Degradation
Continuing to deliver reduced but useful function when a dependency fails, instead of failing the whole request.
Half-Open State
The circuit breaker state that allows a limited number of trial requests through to test whether a failed dependency has recovered.
Incident Command
Assigning explicit roles during an incident — commander, operations lead, communications lead, scribe — so coordination does not compete with diagnosis.
LLM Evaluation
A repeatable measurement of whether an AI system's outputs are good enough, on cases that reflect the actual task.
Quality Attribute Scenario
A structured, testable statement of a non-functional requirement: source, stimulus, environment, artefact, response, response measure.
RTO and RPO
How long recovery may take (RTO) and how much data may be lost (RPO), the two numbers that determine the cost of a resilience design.
Redundancy
Having more instances of a component than the load requires, so that failures can be absorbed without loss of service.
Restore Drill
A scheduled, timed exercise of restoring from backup into a clean environment — the only thing that converts a backup from a hope into a control.
A serverless API works in testing and fails under load with connection errors. The database is at 5% CPU. Explain and fix.
The mechanism Serverless functions scale by creating independent execution environments , each with its own process and its own connection pool. Two hundred con
Leadership asks for multi-region "for resilience". What do you establish before designing anything?
First: is multi region the right answer to the actual problem? Multi region defends against a region wide failure . Most outages are not that — they are bad dep
A downstream service slows from 50 ms to 3 s. Within two minutes every service in the request path is down, including ones that do not call it. Explain the mechanism and how you would have prevented it.
What the interviewer is testing Whether you understand that most outages are amplification, not failure — and whether you can name the specific mechanism rather
A team is launching a new service and asks what its SLO should be. How do you help them decide, and why is "99.99%" usually the wrong first answer?
What the interviewer is testing Whether you treat reliability as a cost benefit decision with a budget, or as a virtue to maximise. Why not four nines It costs
In July 2019 a single regex deployed globally took Cloudflare's network to 100% CPU within seconds. What does this say about how configuration should be released?
The case, as publicly reported On 2 July 2019, Cloudflare deployed a new managed WAF rule. It contained a regular expression that caused catastrophic backtracki
Maersk rebuilt roughly 4,000 servers and 45,000 PCs in about ten days after NotPetya in 2017, and recovered its directory only because one data centre had been offline during the attack. What does this say about DR design?
The case, as publicly reported In June 2017 the NotPetya malware — destructive rather than financially motivated — propagated through Maersk's network, encrypti
Peak trading day is six weeks away and expected to be four times normal traffic. What do you do in those six weeks?
What the interviewer is testing Whether you can run a readiness programme rather than just "add servers", and whether you know what fails at peak that does not
Resilience Testing
Exercising retries, breakers and fallbacks that are otherwise never run.
DR Testing
Restore drills, timed against the stated RTO, into a clean environment.
Game Days
Testing the response — runbooks, access, comms — not only the system.
Contract Testing
Verifying what consumers actually rely on, without a shared environment.
Load Testing
Realistic data, realistic mix, and a ramp rather than a step.
Reliability & Resilience
General material on designing for failure.
Soak Testing
Long runs that surface leaks and slow degradation.
Stress Testing
Pushing past target to learn what breaks first and how it fails.
Testing Strategies
The pyramid, and the contract tests distributed systems add to it.
Availability Mathematics
Series dependencies multiplying, and redundancy that is not independent.
Capacity Planning
What does not autoscale, and the lead-time items that need a date.
Chaos Engineering
Hypothesis-driven failure injection with a bounded blast radius.
Degradation Modes
Deciding in advance what is shed first and what is protected.
Error Budgets
Unreliability as a resource that feature velocity spends.
Failover
Detection latency, promotion, fencing and the cost of failing over wrongly.
Fault Isolation
Cells, zones, tenants and the partitions that bound a failure.
Graceful Degradation
Reduced but useful function when a dependency is gone.
Incident Management
Command roles, severity levels and mitigation before diagnosis.
On-Call
Sustainable rotations, actionable pages and handover discipline.
Postmortems
Finding the systemic conditions, and completing the actions afterwards.
RTO & RPO
How long recovery may take and how much data may be lost.
Redundancy
N+1, N+2 and 2N, correlated failure, and headroom for the failure itself.
Reliability Culture
Blamelessness, error budget policy and reliability as a funded property.