CloudTrail vs CloudWatch: When to Use What? 🕵️‍♂️🔍

This content originally appeared on DEV Community and was authored by Yash Sonawane

“I set up CloudTrail… so why didn’t I get alerted when my instance crashed?”

Ah, the classic confusion! If you’re scratching your head over CloudTrail vs. CloudWatch, you’re not alone.

Both are AWS monitoring tools — but they serve very different purposes. One is like a security camera, the other is like a health monitor. Mixing them up can lead to missed alerts, security blind spots, and a whole lot of frustration.

In this post, I’ll break down both tools using real-world metaphors, easy-to-understand examples, and clear use cases so you’ll never mix them up again.

Let’s decode the difference — once and for all.

CloudTrail = Security Camera for AWS

Imagine CloudTrail as the CCTV system of your AWS account. It records every door opened, button pressed, and switch flipped.

What It Does:

• Logs API calls and events made in AWS
• Tracks who did what, when, and from where
• Answers: “Who deleted my S3 bucket?” or “What changes were made to IAM?”

Example Use Cases:

• Audit all access to your AWS resources
• Detect unauthorized API activity
• Compliance reporting (HIPAA, PCI, etc.)

Example CloudTrail Event:

{
  "eventName": "TerminateInstances",
  "userIdentity": {
    "userName": "devops-admin"
  },
  "sourceIPAddress": "203.0.113.5",
  "eventTime": "2025-07-31T12:34:56Z"
}

Pro Tip: Enable multi-region CloudTrail and send logs to S3 + CloudWatch Logs for long-term retention + alerting.

CloudWatch = Health Monitor for Your Cloud

Think of CloudWatch as your AWS fitbit or pulse checker. It watches your systems in real time — and shouts when something goes wrong.

What It Does:

• Collects metrics, logs, and events from AWS services
• Enables alarms, dashboards, and automated actions
• Answers: “Is my EC2 CPU usage too high?” or “Did my Lambda fail?”

Example Use Cases:

• Monitor server health, disk space, or request latency
• Create alarms (e.g., send an alert when CPU > 80%)
• Set up auto-scaling triggers or restart failed resources

Example CloudWatch Alarm:

{
  "MetricName": "CPUUtilization",
  "Namespace": "AWS/EC2",
  "Statistic": "Average",
  "Period": 300,
  "Threshold": 80,
  "ComparisonOperator": "GreaterThanThreshold"
}

Bonus: CloudWatch can also ingest custom logs — from your app, backend, or any system!

So… CloudTrail or CloudWatch?

Feature	CloudTrail	CloudWatch
Purpose	Audit and governance	Monitoring and performance
Data Type	API activity	Metrics, logs, events
Time Sensitivity	Historical records	Real-time monitoring
Who/What/When	YES	Not really
Health Monitoring
Alerts & Alarms	Via CloudWatch Logs	Built-in

Use CloudTrail when you want to know what happened.
Use CloudWatch when you want to know what’s happening now.

Security Combo: CloudTrail + CloudWatch

Want alerts when someone logs into root? Or deletes a bucket?

Use both:

• CloudTrail logs the event (e.g., DeleteBucket)
• Send logs to CloudWatch Logs
• Create Metric Filters + Alarms to alert you

Example: Alert on Root Login

aws logs put-metric-filter \
  --log-group-name "/aws/cloudtrail/logs" \
  --filter-name "RootLoginAlert" \
  --filter-pattern '{($.userIdentity.type = "Root") && ($.eventName = "ConsoleLogin")}' \
  --metric-transformations metricName=RootLogin,metricNamespace=Security,metricValue=1

TL;DR

Your Turn: What’s YOUR Favorite AWS Monitoring Trick?

CloudTrail and CloudWatch are powerful alone — unstoppable together. Mastering both will save you hours of debugging and prevent costly surprises.

Got a pro tip, cool dashboard setup, or CloudTrail horror story?
Drop it in the comments. Hit if you learned something new, and share this post with a cloud buddy who’s still mixing them up!

Let’s monitor smarter, together.

This content originally appeared on DEV Community and was authored by Yash Sonawane