When we onboard a new client, the first thing we do is a cost audit. Not because we're looking to impress them with a big number — but because it funds everything else. Find the waste, recover the budget, use that budget to do the work right.
Here's the exact 30-minute sequence.
Step 1: Pull the Cost Explorer top-10 (5 min)
Open Cost Explorer, group by Service, sort by cost descending. Look at the top 10 line items. Anything surprising? An EC2 family you don't recognise? An RDS instance that's bigger than your biggest workload should need? Flag those for deeper inspection.
Step 2: Right-sizing report (10 min)
AWS Compute Optimizer is free and criminally underused. Run it, filter to "over-provisioned", sort by estimated monthly savings. The average account we audit has £800–£2,000/month in right-sizing opportunities sitting in this report, untouched.
Step 3: Idle resources (8 min)
Use Trusted Advisor (Business/Enterprise) or Cost Anomaly Detection to find:
- EC2 instances with CPU < 5% over 14 days
- RDS instances with zero connections
- Elastic IPs not attached to running instances (these cost money)
- NAT Gateways in regions with no traffic
Step 4: Reserved Instance coverage (7 min)
Go to the RI Coverage report. Anything below 60% coverage on a stable workload is money left on the table. But — and this is critical — only buy RIs for workloads that have been stable for at least 90 days. The trap is locking in commitments on workloads that're about to be re-architected.
Run this sequence monthly. Block 30 minutes on the last Friday of each month. It compounds.
