Case Study

NAT Gateway Cost Investigation & Optimization

Investigated unexpected NAT Gateway spend by tracing outbound traffic patterns, validating sources, and applying targeted changes (routing, VPC endpoints, and service placement) to reduce recurring network egress cost while keeping reliability intact.

AWS VPC NAT Gateway VPC Flow Logs Cost Explorer VPC Endpoints

High-level diagram of NAT Gateway traffic and cost investigation

1) Problem

NAT Gateway data processing costs were unexpectedly high.
Private workloads were routing traffic to AWS service (e.g., S3/ECR) through NAT.
Goal: reduce NAT usage without breaking production workloads.

2) Architecture

Identified NAT Gateway data processing as the primary cost driver.
Analyzed traffic patterns to determine which AWS service calls were traversing NAT.
Adjusted routing so only true internet-bound traffic continued to use the NAT Gateway.

Architecture diagram showing NAT Gateway placement, traffic paths, and optimizations

3) Outcome

Reduced NAT Gateway data processing by approximately 60%.
Lowered recurring network costs without impacting application availability.
Established a repeatable approach for identifying and mitigating similar cost issues.

Note: Implementation details generalized for confidentiality.