Monitoring & Billing

Once your app is running on AWS, you need to monitor it (is it healthy? fast?) and manage costs (how much are we spending?).

Analogy: Monitoring is like a car’s dashboard — it tells you speed, fuel level, and engine temperature. Billing is like tracking your fuel receipts — you want to know where your money is going.

Amazon CloudWatch collects metrics, logs, and events from AWS resources and your applications.

flowchart TB
    subgraph Sources["Data Sources"]
        EC2_CPU[EC2 CPU/Memory]
        ALB_Requests[ALB Request Count]
        Lambda_Errors[Lambda Error Count]
        Custom_Logs[Custom App Logs]
    end

    subgraph CW["CloudWatch"]
        Metrics[Metrics<br/>CPU, latency, errors]
        Logs[Logs<br/>Application logs]
        Alarms[Alarms<br/>Trigger actions]
        Dashboards[Dashboards<br/>Visualize everything]
    end

    subgraph Actions["Actions"]
        SNS[Send notification<br/>(SNS email/SMS)]
        ASG[Auto Scaling<br/>Add/remove instances]
        Lambda[Run Lambda<br/>Auto-remediate]
    end

    Sources --> CW
    CW --> Actions

    style Sources fill:#3b82f6,color:#fff
    style CW fill:#7c3aed,color:#fff
    style Actions fill:#059669,color:#fff

Useful commands:

# Get CPU metrics
aws cloudwatch get-metric-statistics \
    --namespace AWS/EC2 \
    --metric-name CPUUtilization \
    --dimensions Name=InstanceId,Values=i-123 \
    --start-time 2024-01-01T00:00:00 \
    --end-time 2024-01-02T00:00:00 \
    --period 300 \
    --statistics Average

# Create an alarm
aws cloudwatch put-metric-alarm \
    --alarm-name high-cpu \
    --alarm-description "Alert when CPU > 80%" \
    --metric-name CPUUtilization \
    --namespace AWS/EC2 \
    --statistic Average \
    --period 300 \
    --threshold 80 \
    --comparison-operator GreaterThanThreshold \
    --evaluation-periods 2 \
    --alarm-actions arn:aws:sns:us-east-1:123:my-topic

Key CloudWatch metrics:

Free Tier (12 months):

Cost-saving tips:

1. Right-size EC2 — don’t use m5.xlarge when t3.medium will do
2. Use Spot instances — up to 90% off for fault-tolerant workloads
3. Reserved Instances — 1-3 year commitment, up to 72% off
4. S3 lifecycle policies — move old data to Glacier automatically
5. Delete unused resources — unattached EBS volumes, old snapshots, idle load balancers
6. Use AWS Budgets — set budgets and get alerts when approaching limits

# Check your current costs
aws ce get-cost-and-usage \
    --time-period Start=2024-01-01,End=2024-01-31 \
    --granularity MONTHLY \
    --metrics "BlendedCost" "UnblendedCost" "UsageQuantity"

• CloudWatch = monitoring service — metrics, logs, alarms, dashboards
• Set alarms for key metrics (CPU > 80%, high error rates)
• AWS Free Tier covers basic usage for 12 months — use it to learn
• Right-size instances, delete unused resources, use Spot/Reserved to save money
• Set AWS Budgets alerts so you don’t get surprise bills
• Always monitor costs alongside performance — they’re equally important