Cloud bills are the silent killer of small teams. I have seen startups burn through $50K/year on AWS resources they forgot existed. The worst part? Most of it is preventable with a few hours of auditing.
The 5-Step Cloud Cost Audit
Step 1: Find Your Zombies
Run this simple check across your cloud accounts:
- EC2 instances running for 30+ days with < 5% CPU utilization
- Unattached EBS volumes (you are paying for storage nobody uses)
- Old EBS snapshots (keep the last 7 days, delete the rest)
- Idle load balancers with no target instances
- Forgotten S3 buckets with lifecycle policies set to "keep forever"
Step 2: Right-Size Everything
Most teams over-provision by 3-5x. Check:
- Are your web servers running m5.large when t3.small would do?
- Are your databases on r5.xlarge when t3.medium handles the load?
- Do you have 3 availability zones when 2 would suffice?
Rule of thumb: If average CPU is under 20% for 2 weeks, cut the instance size in half.
Step 3: Use Spot and Reserved Instances
- Spot instances for batch jobs and dev environments: 60-90% savings
- Reserved instances for production workloads: 30-60% savings
- Savings plans for flexible workloads: 20-40% savings
Step 4: Automate Cost Alerts
Set up billing alerts at these thresholds:
- 50% of monthly budget → email to engineering
- 80% of monthly budget → Slack alert to team
- 100% of monthly budget → Page the engineering manager
Step 5: Tag Everything
Without tags, you cannot attribute costs. Require these tags on every resource:
-
Team: Who owns this resource -
Environment: prod, staging, dev -
Project: Which project is this for -
CostCenter: For billing attribution
Real Savings I Have Seen
| Optimization | Monthly Savings | Effort |
|---|---|---|
| Delete 12 zombie EC2 instances | $840 | 2 hours |
| Right-size 8 over-provisioned instances | $1,200 | 4 hours |
| Switch dev env to spot instances | $600 | 3 hours |
| Delete old snapshots (90+ days) | $320 | 1 hour |
| Add lifecycle policies to S3 | $180 | 30 min |
| Total | $3,140/month | ~10 hours |
That is $37,680/year from one weekend of work.
The Cloud Bill Detective Approach
- Export your last 3 months of billing data
- Group by service, then by tag
- Find the top 5 cost categories
- For each, ask: "Do we still need this? Can we reduce it?"
- Set a monthly review calendar invite
Tools That Help
- AWS Cost Explorer: Built-in, free, good for basic analysis
- CloudWatch: Set utilization alarms
- Custom Python script: Query billing API, generate weekly reports
- Spot.io / CAST AI: Automated right-sizing (but costs money)
Want a ready-to-use cloud cost audit checklist, billing alert templates, and a Python script that finds your zombie resources automatically? Check out our Ops Starter Kit:
Stop paying for what you don't use. 💸
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