The Complete Glossary of Uptime Monitoring Terms

Uptime monitoring comes with its own vocabulary. Whether you are new to monitoring or just need a quick reference, this glossary covers every term you will encounter.

A-D

Alert Channel — The notification method used to deliver monitoring alerts (Slack, SMS, email, PagerDuty, webhooks).

Alert Fatigue — The phenomenon where too many alerts cause teams to ignore or miss important notifications.

Availability — The percentage of time a service is operational and accessible. Usually expressed as a percentage (99.9%).

Check Interval — How frequently a monitoring service tests your endpoint. Common intervals range from 30 seconds to 5 minutes.

Cold Start — The initial delay when a serverless function or container starts up after being idle.

Circuit Breaker — A design pattern that stops calling a failing service to prevent cascading failures.

Downtime — Any period when a service is unavailable to users.

E-I

Error Budget — The amount of allowable unreliability defined by your SLO. A 99.9% SLO gives you 0.1% error budget (43 minutes per month).

Escalation Policy — Rules defining who gets notified and when if the primary on-call does not respond.

False Positive — A monitoring alert that fires when no actual problem exists.

Graceful Degradation — Designing systems to maintain partial functionality when components fail.

Heartbeat Monitoring — A check that expects regular pings from your application. If the ping stops, an alert fires. Used for cron jobs and background tasks.

HTTP Monitoring — Checking a URL by sending an HTTP request and verifying the response status code and content.

Incident — An event that causes service degradation or outage requiring response.

K-O

Keyword Monitoring — Checking that a web page contains (or does not contain) specific text. Catches content-level failures that status codes miss.

Latency — The time delay between a request and its response. Usually measured in milliseconds.

MTBF (Mean Time Between Failures) — Average time between incidents.

MTTD (Mean Time to Detect) — Average time from an incident occurring to it being detected by monitoring.

MTTR (Mean Time to Recovery) — Average time from incident detection to full service restoration.

Multi-Region Monitoring — Checking services from multiple geographic locations to detect region-specific outages.

On-Call — A rotation where team members are designated to respond to incidents outside business hours.

P-S

P50/P95/P99 — Percentile response times. P95 means 95% of requests are faster than this value.

Ping Monitoring — Sending ICMP ping packets to check if a host is reachable.

Port Monitoring — Checking if a specific TCP port is open and accepting connections.

Post-Mortem — A blameless review conducted after an incident to identify root causes and preventive actions.

SLA (Service Level Agreement) — A contractual commitment to maintain a certain level of service availability.

SLI (Service Level Indicator) — The actual measured metric used to evaluate service health.

SLO (Service Level Objective) — An internal target for service reliability, stricter than the SLA.

SSL Monitoring — Tracking SSL/TLS certificate validity and expiration dates.

Status Page — A public page displaying the current operational status of your services.

Synthetic Monitoring — Automated tests that simulate user interactions from external locations.

T-Z

TTFB (Time to First Byte) — Time from the request being sent to the first byte of the response being received.

Uptime — The percentage of time a service is available. The inverse of downtime.

Webhook — An HTTP callback triggered by an event. Used for real-time notifications between services.

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