When architecting cloud infrastructure on AWS, optimizing cost, security, and network performance are key concerns. In particular, when private subnets need access to AWS services like S3 or DynamoDB, architects often face a choice:
- Should we use a NAT Gateway?
- Or use VPC Gateway Endpoints?
- Or both?
Let’s explore both scenarios in detail with pros/cons, cost implications, and architectural diagrams.
Scenario 1: With NAT Gateway (No VPC Gateway Endpoint)
Architecture Overview
In this setup:
- Your private subnet cannot access the internet directly.
- A NAT Gateway in the public subnet routes traffic from private resources to the internet.
- For AWS services like S3 or DynamoDB, the traffic goes through the internet (via NAT).
Architecture Diagram
+——————+
| Internet |
+——–+———+
|
+——–v——–+ +—————-+
| NAT Gateway +———> S3/DynamoDB |
+——–+——–+ +—————-+
|
+———–v———–+
| Public Subnet |
| (NAT resides here) |
+———–+———–+
|
+———–v———–+
| Private Subnet |
| EC2 / Lambda / etc. |
+———————–+
Advantages
- Universal internet access: Any service (not just AWS) is reachable.
- No AWS service whitelisting needed—everything routes through the NAT.
Disadvantages
- Higher cost: NAT Gateway is not free. Charges apply for:
- Hourly usage (~$0.045/hour/region)
- Data processing ($0.045/GB)
- Hourly usage (~$0.045/hour/region)
- Potential bottleneck: All outbound traffic from private subnets goes through one NAT unless you scale.
- Security risk: Your data to AWS services (like S3) flows through the internet, even if encrypted.
Cost Summary
| Item | Cost |
| NAT Gateway usage | ~$32.4/month per gateway |
| Data transfer | ~$0.045/GB |
| S3/DynamoDB usage | Regular AWS service cost |
Scenario 2: With VPC Gateway Endpoint (No NAT Gateway)
🔧 Architecture Overview
In this setup:
- You create a Gateway VPC Endpoint for S3 or DynamoDB.
- The traffic never leaves the AWS network—it stays inside the AWS backbone.
- No internet is required to access these services from private subnets.
Architecture Diagram
+————————+
| AWS Backbone |
| (Private connection) |
+———–+————+
|
+———v———-+
| Gateway VPC Endpoint |
+———+———-+
|
+———–v———–+
| Private Subnet |
| EC2 / Lambda / etc. |
+———————–+
✅ Advantages
- Lower cost: No hourly or data processing charges (VPC Gateway Endpoints are free).
- More secure: Data does not traverse the internet.
- Faster: Private AWS backbone usually provides better latency.
❌ Disadvantages
- Limited scope: Only supports S3 and DynamoDB (for Gateway endpoints).
- No internet access: If you also need internet access (e.g., to download packages), a NAT or Internet Gateway is still required.
- Extra setup: Requires configuration of route tables and endpoint policies.
Cost Summary
| Item | Cost |
| VPC Gateway Endpoint | Free |
| S3/DynamoDB usage | Normal pricing |
Use Cases Comparison
| Feature | NAT Gateway | VPC Gateway Endpoint |
| Access to Internet | ✅ Yes | ❌ No |
| Access to AWS Services (S3/DB) | ✅ Yes (via Internet) | ✅ Yes (via AWS backbone) |
| Security | ❌ Less Secure | ✅ More Secure |
| Cost | 💸 High | 💰 Low |
| Setup Complexity | 🔁 Easy to add NAT | 📘 Requires endpoint routing |
| Services Supported | 🌐 Any Internet Service | 🟡 S3 & DynamoDB only |
Hybrid Approach: Both NAT Gateway + VPC Endpoints
You can combine both approaches for best results:
- Use VPC Endpoints for S3/DynamoDB (secure + free).
- Use NAT Gateway for internet-based resources.
This setup reduces cost and boosts security while retaining flexibility.
Conclusion
Choosing between NAT Gateway and VPC Gateway Endpoints depends on your needs:
- If your resources only need to access S3/DynamoDB, Gateway Endpoints are the better, cheaper, and more secure choice.
- If your resources also need internet access, a NAT Gateway is necessary, but be mindful of costs.
For cost-optimized, secure architecture, use VPC Gateway Endpoints as much as possible and limit NAT Gateway usage only to where it’s needed.
