How to Reduce AWS NAT Gateway Costs

By Illusio Platform Engineering Team · Last reviewed: 2026 · 7 min read

AWS NAT Gateways are a necessary component for private subnet egress, but their dual billing model—charging both hourly provisioned uptime and per-GB data processing fees—routinely leads to four- and five-figure invoice surprises.

The Anatomy of AWS NAT Gateway Pricing

NAT Gateway pricing in standard AWS regions consists of two distinct components:

1. Hourly Gateway Charge: Fixed hourly cost for keeping the managed gateway running per availability zone.
2. Data Processing Charge: A fee per gigabyte of traffic that flows through the gateway, regardless of whether that traffic is heading to the public internet, a third-party API, or an AWS service like Amazon S3.

In high-throughput SaaS environments processing terabytes of data daily, the data processing fee accounts for over 90% of total NAT Gateway costs.

Three Architectural Strategies to Eliminate NAT Gateway Waste

1. Enable Free Gateway VPC Endpoints for S3 and DynamoDB

By default, when an EC2 instance or EKS pod in a private subnet communicates with Amazon S3 (e.g. uploading backups, streaming media, or reading data lakes), traffic routes through the VPC NAT Gateway to AWS public endpoints. This incurs standard NAT data processing fees on every single gigabyte.

The Solution: Deploy a Gateway VPC Endpoint for Amazon S3 and Amazon DynamoDB. Gateway VPC Endpoints are completely free of charge from AWS. They inject a direct prefix-list route into your VPC route tables, routing traffic directly across the AWS private network backbone with zero NAT Gateway processing fees.

2. Container Registry Caching & Interface Endpoints

When Kubernetes nodes pull container images from Docker Hub, quay.io, or external public registries during scaling events, image layers pass through the NAT Gateway. Pulling 100GB of container layers across 50 nodes during a deployment spike can generate significant data processing charges.

• Mirror Images to ECR: Store all base images in Amazon Elastic Container Registry (ECR).
• Deploy ECR Interface Endpoints: Deploy VPC Interface Endpoints (AWS PrivateLink) for ECR API and DKR endpoints to ensure image pulls never leave the private network.

3. Eliminating Cross-AZ NAT Routing

A common anti-pattern in multi-AZ architectures is routing traffic from Subnet A (in us-east-1a) through a single NAT Gateway located in Subnet B (in us-east-1b).

This incurs a double billing penalty: you pay standard cross-AZ data transfer fees ($0.01/GB in each direction) plus the NAT Gateway data processing fee. Ensuring traffic routes to a local NAT Gateway in the same Availability Zone eliminates cross-AZ transfer penalties.

Monitoring & Attribution: VPC Flow Logs

To diagnose which specific workloads are driving NAT Gateway spend, enable Amazon VPC Flow Logs aggregated into Amazon CloudWatch Logs or Amazon Athena. Query the bytes field grouped by destination IP and port to immediately isolate high-egress containers or rogue backup scripts.