aws-essentials

AWS Essentials

Production-ready patterns for AWS core services: Lambda handlers, S3 operations, RDS connection management, IAM policies, async messaging, DynamoDB design, CloudFront caching, and cost optimization.

Lambda Handler Patterns

BAD: Unoptimized cold starts, no reuse

// TypeScript - AWS SDK v3
import { DynamoDBClient, PutItemCommand } from '@aws-sdk/client-dynamodb';

export const handler = async (event: any) => {
  const client = new DynamoDBClient({ region: 'us-east-1' }); // ❌ Created every invocation
  const apiKey = 'hardcoded-key-abc123'; // ❌ Hardcoded credentials

  await client.send(new PutItemCommand({
    TableName: 'users',
    Item: { id: { S: event.id }, data: { S: JSON.stringify(event) } }
  }));
};

GOOD: Warm reuse, environment config, structured logging

import { DynamoDBClient, PutItemCommand } from '@aws-sdk/client-dynamodb';
import { SecretsManagerClient, GetSecretValueCommand } from '@aws-sdk/client-secrets-manager';

// ✅ Instantiate outside handler for reuse across warm invocations
const dynamoClient = new DynamoDBClient({ region: process.env.AWS_REGION });
const secretsClient = new SecretsManagerClient({ region: process.env.AWS_REGION });

let cachedSecret: string | null = null;

async function getSecret(): Promise<string> {
  if (cachedSecret) return cachedSecret;

  const response = await secretsClient.send(
    new GetSecretValueCommand({ SecretId: process.env.SECRET_ARN })
  );
  cachedSecret = response.SecretString!;
  return cachedSecret;
}

export const handler = async (event: { id: string; data: Record<string, any> }) => {
  const startTime = Date.now();

  try {
    const secret = await getSecret();

    await dynamoClient.send(new PutItemCommand({
      TableName: process.env.TABLE_NAME!,
      Item: {
        id: { S: event.id },
        data: { S: JSON.stringify(event.data) },
        timestamp: { N: Date.now().toString() }
      }
    }));

    console.log(JSON.stringify({
      level: 'info',
      message: 'Item stored',
      id: event.id,
      duration: Date.now() - startTime
    }));

    return { statusCode: 200, body: JSON.stringify({ success: true }) };
  } catch (error) {
    console.error(JSON.stringify({
      level: 'error',
      message: 'Failed to store item',
      error: error instanceof Error ? error.message : String(error),
      id: event.id
    }));
    throw error;
  }
};