Alarms — Complete Guide
Alarms — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of AWS Cloud Tutorial on Toolliyo Academy.
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AWS Cloud Tutorial · Lesson 65 of 100
Alarms
Core services ✓ → Projects
Projects · 2 — Deploy · ~10 min · AWS — Observability & Security
What is this?
CloudWatch Alarms watch metrics and change state when thresholds breach. They trigger SNS, Auto Scaling, or EventBridge actions.
Why should you care?
AwsVerse pages on-call when payment error rate exceeds 1% for five consecutive minutes.
See it live — copy this example
Run in AWS CloudShell / local AWS CLI v2, or follow the matching steps in the AWS Console (Free Tier).
aws cloudwatch put-metric-alarm \
--alarm-name awsverse-payment-errors \
--metric-name HTTPCode_Target_5XX_Count \
--namespace AWS/ApplicationELB \
--statistic Sum \
--period 60 --evaluation-periods 5 \
--threshold 50 \
--comparison-operator GreaterThanThreshold \
--dimensions Name=LoadBalancer,Value=app/awsverse-alb/abc123 \
--alarm-actions arn:aws:sns:ap-south-1:123:awsverse-oncallWhat happened?
- Alarms when ALB 5xx sum exceeds 50 over five one-minute periods.
- SNS action notifies on-call rotation.
Practice next
- Pick metric with business meaning.
- Set threshold using baseline p99.
- Test alarm with sns subscribe email.
- Add OK action to close incident ticket.
- Use composite alarm for AND conditions.
Remember
Alarms automate response. Use multi-period evaluation. Action to SNS or runbook.
AwsVerse error spike
Bad deploy raises 5xx rate.
Outcome: Alarm fires in 5 min; CodeDeploy rollback triggered via EventBridge.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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