AWS Glossary
Amazon CloudWatch Synthetics
CloudWatch Synthetics runs canaries — scripted probes that periodically check URLs and multi-step journeys — for availability monitoring distinct from deploy canaries.
Definition
Amazon CloudWatch Synthetics runs canaries — scheduled scripts (heartbeat/API or browser) that probe endpoints and user journeys, emit success and latency metrics, and optionally store screenshots/HAR artifacts. Use Synthetics to detect customer-visible outages even when infrastructure metrics look healthy.
When to use it
- Tier-1 journey availability (login, checkout, critical API)
- External measurement to complement Application Signals backend SLOs
- SLA reporting that requires synthetic success ratios
When not to use it
- As a substitute for load testing
- High-frequency browser fleets without a cost owner
- Confused with deploy canaries (progressive delivery) — different concept
Tips
- Prefer API canaries when a full browser is unnecessary
- Page on SuccessPercent with owners/runbooks (monitoring vs alerting)
- Align canary journeys with Application Signals SLOs
Gotchas
Serious
- 1-minute intervals across many canaries dominate CloudWatch spend
- Private VPC misconfig causes false failures
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