Search the practice set
126 questions, 454 terms and 400 topics in 20 areas.
48 results for “Reliability Culture”
Blameless Postmortem
An incident review that seeks the systemic conditions that made a failure possible, explicitly excluding individual fault.
Cost vs Reliability Trade-off
The non-linear relationship between availability and spend, which makes each additional nine roughly an order of magnitude more expensive.
Availability Calculation
Deriving a system's availability from its components, remembering that dependencies in series multiply.
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.
Chaos Engineering
Deliberately injecting failure into a system to discover, before an incident does, which of your resilience assumptions are false.
Disaster Recovery
The plan and capability for restoring service after an event that takes out a whole site, region or system.
Durability vs Availability
Two different storage guarantees — whether data survives, and whether it can be reached right now — routinely conflated because both are quoted in nines.
Error Budget
The amount of unreliability an SLO permits, treated as a resource that feature velocity spends.
FinOps
The practice of giving engineering teams visibility into and accountability for the cost of what they build and run.
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.
Idempotency
The property that performing an operation many times has the same effect as performing it once.
Incident Command
Assigning explicit roles during an incident — commander, operations lead, communications lead, scribe — so coordination does not compete with diagnosis.
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.
Service Level Agreement
A contractual commitment about service level, with a defined remedy — usually a service credit — when it is missed.
Service Level Indicator
The actual measurement of a service's behaviour that an objective is set against — a ratio of good events to valid events.
Service Level Objective
An internal target for a service level indicator, set below the level at which users notice, and used to decide whether to ship or to stabilise.
Severity Levels
A predefined scale of incident impact that determines who is woken, how fast, and what process applies.
Static Stability
The property that a system keeps working on its existing state when its control plane or dependencies are unavailable, rather than needing them to keep running.
Well-Architected Review
A structured self-assessment of a workload against defined pillars — operational excellence, security, reliability, performance, cost, and sustainability.
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
The business asks for "100% uptime" for a new customer portal. Walk me through the conversation that ends in an agreed SLO.
What the interviewer is testing Whether you can run a negotiation that ends in a number both sides own, rather than either capitulating or lecturing about nines
Reliability Culture
Blamelessness, error budget policy and reliability as a funded property.
Cost vs Reliability
Each nine costing an order of magnitude, and pricing the failure instead.
Reliability & Resilience
General material on designing for failure.
Reliability vs Complexity
Mechanisms that add availability and add failure modes.
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.
DR Testing
Restore drills, timed against the stated RTO, into a clean environment.
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.
Game Days
Testing the response — runbooks, access, comms — not only the system.
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.
Resilience Testing
Exercising retries, breakers and fallbacks that are otherwise never run.
SLI, SLO & SLA
The measurement, the internal target, and the contractual commitment.
Static Stability
Serving from existing state when the control plane is unavailable.