Monitoring & DevOps Glossary

Clear definitions for the terms that matter most in uptime monitoring, incident management, and site reliability engineering.

A B C D E F H I L M O P R S T U W

A

Alert Fatigue

A condition where responders become desensitized to alerts due to excessive volume or frequent false positives.

Availability

The proportion of time a system is functional and accessible, often expressed as a percentage.

Auto-Scaling

The automatic adjustment of compute resources based on current demand to maintain performance and control costs.

Apdex Score

A standardized metric that rates user satisfaction with application response time on a scale from 0 to 1.

API Monitoring

The practice of monitoring API endpoints for availability, performance, correctness, and compliance with expected behavior.

Alert Routing

The process of directing alerts to the appropriate team or individual based on rules, service ownership, and severity.

B

Blue-Green Deployment

A deployment strategy using two identical production environments, where traffic is switched from the current (blue) to the new (green) version.

Black-Box Monitoring

Monitoring a system from the outside, testing externally visible behavior without knowledge of internal implementation.

Blameless Postmortem

An incident review process that focuses on systemic improvements rather than individual fault.

C

Cron Job

A scheduled task that runs automatically at specified intervals, defined using a cron expression.

Canary Deployment

A deployment strategy that rolls out changes to a small subset of users before a full release to detect issues early.

Circuit Breaker

A software pattern that prevents cascading failures by temporarily stopping requests to a failing service.

Chaos Engineering

The practice of intentionally injecting failures into a system to test its resilience and uncover weaknesses.

D

Downtime

A period when a system or service is unavailable or not functioning correctly for its users.

DORA Metrics

Four key metrics identified by the DORA team for measuring software delivery performance: deployment frequency, lead time, change failure rate, and MTTR.

DevOps

A culture and set of practices that unify software development and IT operations to deliver software faster and more reliably.

DNS Monitoring

Monitoring that checks DNS resolution to ensure domain names resolve correctly and within acceptable time.

E

Escalation Policy

A set of rules defining how alerts are routed and escalated when the primary responder does not acknowledge them in time.

Error Budget

The maximum amount of unreliability a service can have within a given period, derived from the SLO.

F

Five Nines (99.999% Uptime)

A reliability standard allowing no more than 5 minutes and 15 seconds of downtime per year.

Failover

The automatic switching to a backup system when the primary system fails, ensuring service continuity.

H

Health Check

An endpoint or process that verifies whether a service or its dependencies are functioning correctly.

HTTP Status Code

A three-digit code returned by a web server indicating the result of the client's request.

I

Incident Management

The process of detecting, responding to, resolving, and learning from service disruptions.

Incident Severity

A classification system that categorizes incidents by their impact and urgency to prioritize response efforts.

L

Latency

The time delay between a request being sent and the response being received, typically measured in milliseconds.

Load Balancing

The distribution of incoming network traffic across multiple servers to ensure no single server is overwhelmed.

M

MTTR (Mean Time to Recover)

The average time it takes to restore a system or service after a failure or incident.

MTTA (Mean Time to Acknowledge)

The average time between an alert being triggered and a responder acknowledging it.

MTTF (Mean Time to Failure)

The average time a non-repairable system or component operates before it fails.

MTBF (Mean Time Between Failures)

The average time between consecutive failures of a repairable system.

MTTD (Mean Time to Detect)

The average time between the onset of a problem and its detection by monitoring or human observation.

Maintenance Window

A scheduled period during which a system is intentionally taken offline or degraded for updates, patches, or infrastructure changes.

O

On-Call

A rotation system where team members are designated to respond to alerts and incidents outside normal working hours.

Observability

The ability to understand the internal state of a system by examining its external outputs: logs, metrics, and traces.

On-Call Rotation

A schedule that determines which team member is the primary responder for alerts during each time period.

P

Post-Mortem (Incident Review)

A structured review conducted after an incident to identify root causes and prevent recurrence.

P99 Latency

The response time below which 99% of requests are served — used to measure tail latency and worst-case user experience.

R

Runbook

A documented set of procedures for diagnosing and resolving specific types of incidents or operational tasks.

RTO (Recovery Time Objective)

The maximum acceptable duration of time a service can be offline after a disaster or failure before causing unacceptable business impact.

RPO (Recovery Point Objective)

The maximum acceptable amount of data loss measured in time — how far back in time your recovery point can be.

Redundancy

The duplication of critical system components to increase reliability and eliminate single points of failure.

Response Time

The total time elapsed between sending a request and receiving the complete response from a server.

Root Cause Analysis (RCA)

A systematic investigation technique used to identify the fundamental cause of an incident, not just its symptoms.

S

SLA (Service Level Agreement)

A formal contract defining the expected level of service, including uptime guarantees, between a provider and customer.

SLO (Service Level Objective)

An internal target for service reliability, typically more ambitious than the external SLA.

SLI (Service Level Indicator)

A quantitative measure of a specific aspect of service reliability, such as availability, latency, or error rate.

Status Page

A public-facing page that communicates the current operational status of a service to users and stakeholders.

Synthetic Monitoring

Proactive monitoring that simulates user interactions to test service availability and performance from external locations.

SSL Certificate

A digital certificate that authenticates a website's identity and enables encrypted HTTPS connections.

SRE (Site Reliability Engineering)

A discipline that applies software engineering practices to infrastructure and operations to build scalable and reliable systems.

Service Mesh

A dedicated infrastructure layer for handling service-to-service communication in microservice architectures.

T

Toil

Repetitive, manual operational work that scales linearly with service growth and can be automated.

Throughput

The rate at which a system processes requests or data, typically measured in requests per second.

TCP Monitoring

Monitoring that checks the availability and response time of services by establishing TCP connections to specific ports.

TLS Handshake

The initial negotiation process between a client and server that establishes an encrypted HTTPS connection.

U

Uptime

The percentage of time a system or service is operational and accessible to users.

Uptime SLA

The specific uptime percentage guaranteed in a service level agreement, defining maximum allowable downtime.

W

Webhook

An HTTP callback that sends real-time data to a specified URL when a specific event occurs.

White-Box Monitoring

Monitoring based on internal system metrics, logs, and traces that reveal the internal state and behavior of a service.

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