What should I use for alerting on app outages without noise?

For alerting on app outages without lots of noise, the best default is:

Use SLO-based alerting with symptom-based signals

Instead of alerting on every server metric, alert on whether users are actually impacted.

Good alert sources

• Availability SLO burn rate
  Example: “5xx rate is consuming error budget too fast.”
• Latency SLO burn rate
  Example: “p95/p99 latency is high enough that users are failing.”
• Synthetic checks / uptime probes
  Example: “Login page or API endpoint is failing from multiple regions.”
• Critical dependency failures
  Example: “Payments API down,” but only for truly user-facing dependencies.

Avoid as primary alerts

• CPU, memory, disk, pod restarts
• Single-instance failures
• One-off 5xx spikes
• Alerts from every service in a chain

Those are useful for debugging or dashboards, but they’re often noisy as paging alerts.

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A practical low-noise setup

1. Page only on user-impacting conditions

Examples:

• “More than 2% of requests are failing for 5 minutes”
• “Latency p95 > X for 10 minutes on a critical endpoint”
• “Synthetic check fails from 2 regions for 3 consecutive runs”

2. Use burn-rate alerts

Common pattern:

• Fast burn: catches severe outages quickly
• Slow burn: catches smaller but sustained issues

This is one of the best ways to reduce noise while still catching real incidents early.

3. Separate paging vs ticket alerts

• Paging: only urgent, customer-facing, actionable problems
• Ticket/Slack: lower severity signals, warnings, capacity issues

4. Deduplicate and group alerts

• One incident = one page
• Group by service / endpoint / SLO
• Suppress cascades from downstream failures

5. Alert on symptoms, not causes

For example:

• Page on “checkout failing”
• Don’t page separately for DB CPU high, cache miss spike, pod restart, unless they directly map to customer impact

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Recommended tools/patterns

You can implement this with:

• Prometheus + Alertmanager for metrics and routing
• Grafana Cloud / Datadog / New Relic if you want managed observability
• Synthetics for simple uptime and critical path checks
• Error budget/SLO tooling like Sloth, Pyrra, or vendor SLO features

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Simple rule of thumb

If an alert would make a user say “do I care right now?”, it belongs in paging.
If it’s mainly useful for engineers investigating or planning, don’t page on it.

If you want, I can suggest a minimal alert policy for a web app or API (with exact thresholds and examples).