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#nat-gateway

2 stories

Cloud & Infrastructure Bug Report

EC2 in a new private subnet cannot reach the internet or SSM: missing route table association

John Nguyen · May 27, 2026 · 10 min read

Instances in a freshly added private subnet timed out on dnf and never showed up in Session Manager, while identical instances in older subnets were fine. The subnet had silently fallen back to the VPC main route table, which had no NAT route.

Banner: AWS NAT Gateway bill spike caused by S3 and ECR traffic from private subnets

Cloud & Infrastructure Bug Report

AWS NAT Gateway bill spike from S3 and ECR traffic in private subnets

Daniel Tran · Aug 26, 2025 · 9 min read

Our AWS bill jumped by over 9,000 USD in one month and nothing looked broken. The cause was NAT Gateway data processing: batch jobs in private subnets were reading S3 and pulling ECR images through NAT. VPC endpoints cut that line item by 94 percent.