AWS Lambda API

I built a serverless voting API with AWS Lambda and API Gateway. Zero servers to manage.

exports.handler = async (event) => {
    const { httpMethod, body, headers } = event;

    // CORS handling
    const corsHeaders = {
        'Access-Control-Allow-Origin': '*',
        'Access-Control-Allow-Headers': 'Content-Type',
        'Access-Control-Allow-Methods': 'GET, POST, OPTIONS'
    };

    if (httpMethod === 'OPTIONS') {
        return { statusCode: 200, headers: corsHeaders };
    }
};
            

API Gateway routes requests to Lambda functions. DynamoDB stores vote data.

// DynamoDB integration
const AWS = require('aws-sdk');
const dynamodb = new AWS.DynamoDB.DocumentClient();

const params = {
    TableName: 'project-votes',
    Key: { projectId: 'terrellflautt-portfolio' },
    UpdateExpression: 'ADD voteCount :val',
    ExpressionAttributeValues: { ':val': 1 },
    ReturnValues: 'UPDATED_NEW'
};

const result = await dynamodb.update(params).promise();
            

Cost: $0.00. Handles 1M requests monthly on free tier.

Auto-scaling built-in. No capacity planning needed.

// Rate limiting with DynamoDB
const rateLimit = {
    TableName: 'rate-limits',
    Key: { ip: clientIP },
    UpdateExpression: 'ADD requestCount :val',
    ExpressionAttributeValues: { ':val': 1 },
    ReturnValues: 'UPDATED_NEW'
};

if (result.Attributes.requestCount > 10) {
    return { statusCode: 429, body: 'Rate limited' };
}
            

Deployment through CloudFormation:

Resources:
  VotingFunction:
    Type: AWS::Lambda::Function
    Properties:
      Runtime: nodejs18.x
      Handler: index.handler
      Code:
        ZipFile: |
          exports.handler = async (event) => {
            // Function code here
          };

  VotingApi:
    Type: AWS::ApiGateway::RestApi
    Properties:
      Name: voting-api

  VotingDeployment:
    Type: AWS::ApiGateway::Deployment
    Properties:
      RestApiId: !Ref VotingApi
      StageName: prod
            

Infrastructure as code. Version controlled. Reproducible deployments.

Cold start optimization:

// Keep connections warm
let dynamodb;

exports.handler = async (event) => {
    if (!dynamodb) {
        dynamodb = new AWS.DynamoDB.DocumentClient();
    }
    // Use existing connection
};
            

Response time: 100ms average. 50ms when warm.

Monitoring with CloudWatch. Errors trigger SNS notifications automatically.