1Connecting AWS Lambda functions to AWS services like Amazon ElastiCache and DynamoDB can be achieved in multiple ways, depending on the specific architecture and networking configurations. In scenarios where you want to avoid using a NAT Gateway due to cost or simplicity concerns, there are alternative approaches you can take. This article explores how to connect AWS Lambda to both Amazon ElastiCache and DynamoDB without relying on a NAT Gateway.
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3## Key Concepts
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5AWS Lambda functions run in a VPC if they need access to resources that are only accessible inside a VPC, such as ElastiCache or an RDS instance. However, when a Lambda function is associated with a VPC, it doesn't have default internet access because it lacks a public IP/DNS name. NAT Gateways are commonly used to allow VPC-based designs to access AWS services directly, but there are alternatives for specific services like DynamoDB and ElastiCache.
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7### Connecting to DynamoDB
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9AWS DynamoDB is a fully-managed NoSQL database service that doesn't require NAT for Lambda connections thanks to a feature called **VPC Endpoints** (specifically, Interface VPC Endpoints for DynamoDB). 
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11#### Steps to Connect
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131. **Create a VPC Endpoint for DynamoDB:**
14   - Go to the AWS Management Console.
15   - Navigate to the **VPC** service.
16   - Select **Endpoints** and then **Create Endpoint**.
17   - Select the service category **AWS Services** and search for `com.amazonaws.<region>.dynamodb`.
18   - Choose the VPC and subnets to associate with this endpoint.
19   - Modify the security group to allow the necessary traffic.
20
212. **Update Lambda Function:**
22   - Ensure your Lambda function is associated with the same VPC, subnets, and security groups.
23
243. **Modify IAM Policies:**
25   - The Lambda function needs IAM permissions to use the DynamoDB operations. Attach the necessary policies such as:
26```json
27     &#123;
28       "Version": "2012-10-17",
29       "Statement": [
30         &#123;
31           "Effect": "Allow",
32           "Action": "dynamodb:*",
33           "Resource": "*"
34         &#125;
35       ]
36     &#125;