How to Optimize AWS NAT Gateway Costs

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How to Optimize AWS NAT Gateway Costs

Practical Strategies for EKS & Private Subnet Workloads

AWS NAT Gateway is one of the most commonly overlooked cost centers in AWS — especially when running EKS, private node groups, and RDS in private subnets.

NAT costs grow silently because they are driven by:

• Hourly NAT charges
• Per-GB data processing fees
• Architectural defaults that scale cost faster than traffic

This article explains why NAT costs spike, how to reduce them, and how AWS’s new Regional NAT Gateway changes the game.

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Why NAT Gateway Costs Spike

NAT Gateway charges you for:

• Every hour the gateway exists
• Every GB of data processed, regardless of destination

In EKS environments, NAT is commonly used for:

• Pulling images from ECR
• STS calls (IRSA / Pod Identity)
• CloudWatch logs
• Secrets Manager
• SQS / SNS
• External API calls

Most teams don’t realize how much of this traffic never needed NAT in the first place.

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What You’re Really Paying For

A classic setup looks like this:

• 1 NAT Gateway per Availability Zone
• Private subnets route 0.0.0.0/0 → NAT
• Even low-traffic AZs still incur full hourly cost

Result:

• High baseline spend
• NATs sitting idle but still billing
• Dev & staging environments paying prod-level network costs

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Core NAT Cost Optimization Strategies

1️⃣ Use VPC Endpoints to Bypass NAT (Highest ROI)

Most NAT traffic is actually AWS service traffic, not “internet” traffic.

Use:

• Gateway endpoints (FREE)
  • S3
  • DynamoDB
• Interface endpoints (PrivateLink)
  • ECR (api + dkr)
  • STS
  • Secrets Manager
  • CloudWatch Logs
  • SQS / SNS
  • API Gateway (private APIs)

Once endpoints are in place:

• Traffic stays inside AWS
• NAT data processing drops sharply
• Security improves automatically

This alone often reduces NAT costs by 40–70%.

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2️⃣ Reduce Unnecessary Egress Through NAT

Common NAT abusers:

• Repeated external API calls
• Public image registries
• OS package updates
• Large downloads during startup

Optimizations:

• Cache artifacts in S3
• Use ECR instead of public registries
• Batch external calls
• Avoid cross-AZ NAT routing

Less data → less NAT cost.

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3️⃣ Right-Size NAT for the Environment

Not every environment needs:

• Multi-AZ NAT
• Full HA
• Always-on NAT capacity

For:

• Dev / test
• Staging
• Internal tools

You can safely optimize availability assumptions to reduce spend.

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🆕 New Update: AWS Regional NAT Gateway

This is a major shift in AWS networking economics.

The Old Model (Per-AZ NAT)

• One NAT Gateway per AZ
• High hourly cost multiplied by AZ count
• Recommended mainly for availability, not efficiency

The New Model (Regional NAT Gateway)

• Single NAT Gateway per VPC (region-wide)
• Serves private subnets across all AZs
• Eliminates the need to deploy NAT in every AZ

Why This Matters

• Cuts NAT hourly cost by ~60–70%
• Simplifies routing
• Ideal for EKS workloads already using VPC endpoints

Trade-Off to Understand

• Traffic from other AZs may incur cross-AZ data transfer
• Still usually cheaper than running multiple idle NATs
• For ultra-critical workloads, per-AZ NAT may still make sense

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Best-Practice Pattern (Modern EKS Setup)

The most cost-efficient architecture today:

• ✅ VPC endpoints for all AWS services
• ✅ Regional NAT Gateway for true internet traffic
• ✅ Per-AZ NAT only when strict AZ isolation is required

This keeps NAT usage minimal, intentional, and predictable.

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Monitoring & Validation

To ensure savings:

• Track NAT Gateway data processing in Cost Explorer
• Use VPC Flow Logs to identify NAT-heavy sources
• Compare pre/post endpoint rollout traffic
• Validate cross-AZ charges vs NAT hourly savings

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Final Takeaway

AWS didn’t reduce NAT pricing.

They gave you architectural flexibility.

If you’re still running:

• One NAT per AZ
• No VPC endpoints
• Private EKS clusters with heavy AWS API usage

You’re almost certainly overpaying.

Modern NAT cost optimization is about:

• Avoiding NAT, not scaling it
• Using endpoints first
• Choosing regional vs per-AZ NAT intentionally

Small networking changes now have big FinOps impact later.

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