A Sydney marketplace's cloud bill had climbed every month for a year while its traffic barely moved. Each team suspected another team's service, and nobody had time to look.
In the first week, the review also found a storage bucket of supplier contracts that anyone with the link could read.
- Read the bill before cuttingEngineers tagged every resource to an owner and read twelve months of cost data before switching anything off.
- Close the real leaksStorage traffic was crossing a NAT gateway at a per-gigabyte charge, so a free gateway endpoint now carries it. Debug logging ran at full volume in production and now samples. Old snapshots had no expiry and now do.
- Lock the bucket the same dayThe contracts bucket was closed within the hour, and its access logs were kept to show who had read it.
- Every change reviewedEach change went through infrastructure code, reviewed by an engineer and approved by the client's platform lead, with a rollback ready.
resource "aws_vpc_endpoint" "s3" { vpc_id = aws_vpc.main.id service_name = "com.amazonaws.ap-southeast-2.s3" vpc_endpoint_type = "Gateway"}resource "aws_s3_bucket_public_access_block" "contracts" { bucket = aws_s3_bucket.contracts.id restrict_public_buckets = true}- Cost trace61% of NAT data-processing charges come from S3 traffic leaving the private subnets.
- EngineerAdded an S3 gateway endpoint, which carries no data charge, and blocked public access on the contracts bucket.
- Your platform leadApproved and applied with the rollback plan open.