Reliability Glossary

Browse 91 reliability terms defined in plain English, from the cultural dictionary of computing.

91 Reliability Terms

ACID
An acronym for the four properties that guarantee reliable database transactions: Atomicity (all or nothing), Consistency (data stays valid), Isolation...
Active-Active
Active-Active is a high-availability architecture pattern where two or more servers or data centers simultaneously handle production traffic, as opposed to...
AI Benchmark
An evaluation concept used to measure, inspect, or compare model behavior through ai benchmark. It influences how models are trained, evaluated, or served, and...
AI Fairness
An evaluation concept used to measure, inspect, or compare model behavior through ai fairness. It influences how models are trained, evaluated, or served, and...
AI Hallucination
An evaluation concept used to measure, inspect, or compare model behavior through ai hallucination. It influences how models are trained, evaluated, or served,...
AI Hallucination Rate
A measured estimate of how often an AI system produces false, invented, or unsupported claims in a given task setup.
Availability Zone
A physically separate data center within a cloud region, with independent power, cooling, and networking. Deploying across multiple AZs provides high...
blast radius
The scope of impact when a failure, misconfiguration, or security breach occurs — how many users, services, or systems are affected. Good architecture...
blue-green deployment
A deployment strategy that maintains two identical production environments: 'blue' (current live) and 'green' (new version). Traffic is switched from blue to...
Bullet Proof
A casual way to say something seems extremely robust, reliable, or hard to break. In engineering slang, it is often used optimistically, sometimes more...
Canary Analysis
Automated statistical comparison between a canary deployment (new version, small traffic percentage) and the baseline (current version) to detect regressions...
canary release
A deployment strategy where a new version is rolled out to a small subset of users or servers first, then gradually expanded if metrics look healthy. Named...
Chaos Budget
The amount of risk a team is willing to take with chaos experiments, analogous to error budgets. When reliability is high (error budget surplus), the chaos...
Chaos Monkey
A tool created by Netflix that randomly terminates production instances to ensure that engineers build resilient services that can tolerate unexpected...
Chaos Monkey Culture
A reliability mindset that values failure testing, resilience drills, and systems that can tolerate component loss under realistic conditions.
Chaos Testing
Deliberately injecting failures (network partitions, server crashes, disk full, clock skew, high latency) into a system to verify it handles them gracefully....
circuit breaker
A design pattern that prevents an application from repeatedly trying to execute an operation that is likely to fail, by 'tripping' after a threshold of...
Core Service
A service that plays a central role in a platform and is widely depended on by other services, jobs, or customer-facing features. Core services usually require...
Dead Letter Queue
A special queue where messages that can't be processed (after exceeding retry limits) are stored for later analysis instead of being discarded. Prevents poison...
Defensive Coding
Writing code to guard against bad input, misuse, edge cases, and unexpected states rather than assuming everything upstream behaves perfectly. It often...
Defensive Programming
A coding approach that assumes inputs, state, and dependencies may be invalid or hostile and therefore validates, bounds, and handles errors carefully. In...
Downtime
A period when a system, service, or component is unavailable or not functioning as intended for users. It is one of the most direct signals of operational...
Downtime Culture
A team's shared attitude toward outages, maintenance windows, and service interruptions, including what is tolerated, communicated, and learned from. Downtime...
Error Boundary
An Error Boundary is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
error budget
The acceptable amount of unreliability for a service over a given period, calculated as 1 minus the SLO. A service with a 99.9% availability SLO has a 0.1%...
Error Budget
The allowed amount of unreliability based on SLO targets — if your SLO is 99.9% availability, your error budget is 0.1% (about 43 minutes per month). When the...
Error Budget Culture
A culture that takes error budgets seriously as a way to balance reliability and change velocity. In healthy teams, error budget culture means service quality...
Error Code
An Error Code is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code easier...
Error Correction
An Error Correction is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Error Handling
An Error Handling is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Error Recovery
An Error Recovery is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code...
Error Type
An Error Type is a development concept used to shape how software is built, executed, or maintained in real systems. Developers rely on it to make code easier...
Evaluation Metric
An evaluation concept used to measure, inspect, or compare model behavior through evaluation metric. It influences how models are trained, evaluated, or...
Factuality
An evaluation concept used to measure, inspect, or compare model behavior through factuality. It influences how models are trained, evaluated, or served, and...
Failover
Failover is the automatic or manual process of switching to a redundant system, server, network, or component when the primary one fails, ensuring continuous...
Failure Analysis
The systematic investigation of why something failed, with the goal of understanding causes, contributing factors, and improvements. In engineering culture...
Failure Mode
A specific way in which a system, process, or component can fail. In engineering culture, thinking in failure modes helps teams prepare for real breakage...
Fairness Metric
An evaluation concept used to measure, inspect, or compare model behavior through fairness metric. It influences how models are trained, evaluated, or served,...
Fault Tolerant Culture
A culture that assumes failures will happen and therefore values resilience, redundancy, graceful degradation, and calm recovery rather than magical thinking....
Five Nines
A measure of system availability equal to 99.999%, allowing no more than 5 minutes and 15 seconds of downtime per year.
Flake
A test, build, or job that passes and fails intermittently without a meaningful code change, usually because of timing, environment variance, hidden...
Flaky
Unreliable or inconsistent in a way that passes sometimes and fails other times without a meaningful code change. The term is most often used for tests,...
Game Day
A planned exercise where teams simulate failures, incidents, or unusual conditions to practice response and test resilience. In operations culture game days...
Hallucination Mitigation
An evaluation concept used to measure, inspect, or compare model behavior through hallucination mitigation. It influences how models are trained, evaluated, or...
Health Check
An endpoint (typically /health or /healthz) that reports whether a service is running and ready to accept traffic. Used by load balancers, orchestrators, and...
Heroic Engineering
A culture that relies on last-minute heroics, individual rescue acts, and unsustainable effort instead of resilient systems and planning.
Human Evaluation
An evaluation concept used to measure, inspect, or compare model behavior through human evaluation. It influences how models are trained, evaluated, or served,...
idempotency
The property where performing an operation multiple times produces the same result as performing it once. In APIs, idempotent operations are safe to retry...
Idempotency Key
A unique token sent with an API request to ensure that retrying the same operation produces the same result without side effects. Critical for payment APIs and...
Idempotent
An operation that produces the same result whether executed once or multiple times. Critical in distributed systems where network failures mean you might...
Idempotent Pipeline
A data pipeline that produces the same output regardless of how many times it's run with the same input. Achieved through techniques like UPSERT/MERGE,...
Incident Post-Mortem
A structured analysis written after an outage or operational failure to document timeline, impact, root causes, contributing factors, and follow-up actions....
Just Works
A simpler shorthand for saying a tool or system behaves with satisfying reliability and low friction. In engineering slang, people love the phrase because...
LLM Reliability
The extent to which a large language model system behaves consistently and acceptably across repeated use, edge cases, and operational conditions. Reliability...
Load Shedding
The deliberate rejection of a portion of incoming requests when a system is under extreme load, preserving capacity to successfully serve the remaining traffic...
MTBF
Mean Time Between Failures. The average time a repairable system operates between successive failures, calculated as total uptime divided by the number of...
MTTF
Mean Time To Failure. The average time a non-repairable component or system operates before it fails for the first time.
MTTR
Mean Time To Recovery (or Repair). The average elapsed time from when a failure is detected to when the system is fully restored to normal operation.
Nines
Shorthand for uptime percentages. 'Three nines' = 99.9%, 'five nines' = 99.999%. Each additional nine is exponentially harder and more expensive to achieve....
Oncall Burnout
Exhaustion caused by repeated pager duty, interrupted sleep, constant incident pressure, or poor production hygiene.
On-Call Culture
The norms and expectations surrounding pager duty, incident ownership, and how teams support engineers who handle production issues.
Ounce of Prevention
A proverb-style reminder that a little preventive work can save a lot of later pain. In engineering slang, it usually gets invoked when someone is arguing for...
Outbox Pattern
A pattern for reliable event publishing in microservices: instead of directly publishing to a message broker (which can fail independently of the database),...
Packet Loss
The failure of one or more network packets to reach their destination, caused by congestion, faulty hardware, signal degradation, or deliberate QoS dropping....
postmortem
A structured document written after an incident that analyzes what happened, why, and how to prevent recurrence. Good postmortems are blameless (focusing on...
Postmortem Culture
The way a team handles incident reviews, including whether postmortems are blameless, useful, and tied to real follow-through.
Post-Mortem Culture
The shared norms around how an organization investigates failures after they happen, including whether reviews are blameful or learning-oriented and whether...
Production Incident
A failure or degradation in a live system that affects real users, business operations, or service reliability. The term usually implies formal response,...
Production Ready
Good enough to run for real users under real operational conditions, with acceptable reliability, observability, security, and support characteristics. Teams...
Replication
The process of copying and maintaining data across multiple database instances or nodes so that every replica holds the same information, improving...
Retry Storm
A cascading failure where many clients simultaneously retry failed requests, overwhelming an already struggling service and preventing it from recovering —...
Robustness
The ability of an AI system to remain useful and stable across noisy inputs, edge cases, shifting conditions, and small perturbations. Robustness matters...
Safety-Critical
Describing a system whose failure could result in loss of life, significant injury, or major environmental damage, requiring rigorous verification, formal...
Service Level
A defined standard for performance, availability, response time, or other operational commitments in a service relationship. Service levels matter because...
Single Point of Failure Slang
Informal language for any person, service, component, or process whose failure can take down a larger system. In engineering slang, calling something a single...
Site Reliability
The discipline of keeping services reliable through engineering approaches to operations, including automation, observability, incident response, and...
Six Nines
A shorthand boast or target for extremely high availability, roughly 99.9999 percent uptime. In engineering slang, six nines often carries a skeptical tone...
SLA
Service Level Agreement — a formal commitment defining the expected level of service (usually uptime). 99.9% sounds great until you realize it allows 8.7 hours...
Sled Dog
A dependable system or person that keeps pulling heavy operational load without much glamour. In engineering slang, a sled dog is respected because the boring...
SLI
Service Level Indicator — a carefully chosen metric that quantitatively measures some aspect of a service's reliability, such as request latency, error rate,...
SLI/SLO/SLA
Three related reliability concepts: SLI (Service Level Indicator) is the metric measured (e.g., request latency p99). SLO (Service Level Objective) is the...
SLO
Service Level Objective — a target value or range for a service's reliability, expressed as a percentage (e.g., 99.9% availability). SLOs provide a...
Software Testing
The practice of executing software under controlled conditions to verify that it behaves as expected and to discover defects. Encompasses multiple levels —...
SRE
Site Reliability Engineering (SRE) is a discipline, originated at Google, that applies software engineering principles to infrastructure and operations. SRE...
Status Page Culture
The norms around how openly and accurately a company communicates outages, degradation, and incident progress to customers.
Structured Output AI
An AI pattern where responses are constrained to a defined structure such as JSON, a schema, or typed fields.
TCP
TCP, or Transmission Control Protocol, is a connection-oriented transport protocol that provides reliable, ordered delivery of data between applications over...
Transaction
A sequence of database operations treated as a single atomic unit — either all succeed (commit) or all are rolled back. Transactions provide ACID guarantees:...
Trust but Verify
A principle that accepts cooperation or assumptions provisionally but still requires evidence, checks, or monitoring before relying on them completely....
Warm Standby
A redundancy approach where a secondary system is running and receiving data updates but is not serving live traffic, allowing it to be promoted to primary...
Webhook Retry
The retry policy used when a webhook delivery fails (non-2xx response or timeout). Good implementations use exponential backoff (e.g., 1min, 5min, 30min, 2hr,...

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