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
| Scenario | Use |
|---|---|
| Who created a resource? | CloudTrail |
| EC2 CPU at 95%? | CloudWatch |
| Log every IAM change? | CloudTrail |
| Trigger alarm on Lambda failure? | CloudWatch |
| Setup for compliance audit? | CloudTrail |
| Monitor app error logs? | CloudWatch |
💬 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
Yash Sonawane | Sciencx (2025-08-12T01:51:00+00:00) CloudTrail vs CloudWatch: When to Use What? 🕵️♂️🔍. Retrieved from https://www.scien.cx/2025/08/12/cloudtrail-vs-cloudwatch-when-to-use-what-%f0%9f%95%b5%ef%b8%8f%e2%99%82%ef%b8%8f%f0%9f%94%8d/
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