Monitoring and Billing

Understanding how to monitor your AWS resources and manage costs is just as important as knowing how to build with them. AWS provides comprehensive tools for observability, alerting, and cost management.

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Amazon CloudWatch

CloudWatch is the primary monitoring and observability service in AWS. It collects metrics, logs, and events from AWS resources.

Metrics

CloudWatch automatically collects metrics from AWS services:

Service	Example Metrics
EC2	CPU utilisation, network in/out, disk reads/writes
RDS	Database connections, read/write latency, free storage
S3	Number of objects, bucket size, request count
Lambda	Invocations, duration, errors, throttles

Alarms

CloudWatch Alarms let you define thresholds and take action when metrics exceed them:

• OK — the metric is within the threshold
• ALARM — the metric has exceeded the threshold
• INSUFFICIENT_DATA — not enough data to evaluate

Example alarm: If EC2 CPU utilisation exceeds 80% for 5 minutes, send an email via SNS.

Logs

CloudWatch Logs collects and stores log files from:

• EC2 instances (via the CloudWatch agent)
• Lambda functions (automatically)
• API Gateway, VPC Flow Logs, Route 53 queries, and more

You can search, filter, and create metrics from log data.

Dashboards

CloudWatch Dashboards provide customisable visualisations of your metrics. You can create dashboards that show:

• Real-time graphs of key metrics
• Alarm status across multiple resources
• Cross-region and cross-account data

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AWS CloudTrail

While CloudWatch monitors performance, CloudTrail monitors activity. CloudTrail records API calls made to your AWS account.

What CloudTrail Tracks

• Who made the call (IAM user, role, or service)
• What API was called (e.g., RunInstances, CreateBucket)
• When the call was made
• Where the call originated (source IP address)

Use Cases

• Security auditing — who changed a security group?
• Compliance — prove that resources were configured correctly
• Troubleshooting — what action caused the issue?

CloudTrail stores events for 90 days by default. For longer retention, configure a trail to deliver logs to an S3 bucket.

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AWS Cost Management

AWS Pricing Models

Most AWS services follow one of these pricing models:

Model	Description	Example
Pay-as-you-go	Pay only for what you use	EC2 on-demand, Lambda
Reserved	Commit for 1-3 years for discounts	EC2 Reserved Instances
Volume-based	Price decreases as usage increases	S3 storage tiers
Free tier	Free usage within limits	750 hrs EC2 t2.micro/month

AWS Billing Dashboard

The Billing Dashboard shows: