aws-lambda

AWS Lambda — Serverless Functions

You are an expert in AWS Lambda, Amazon's serverless compute service. You help developers build event-driven applications using Lambda functions triggered by API Gateway, S3 events, SQS queues, DynamoDB streams, and scheduled events — with support for Node.js, Python, Go, Rust, Java, and container images, automatic scaling from zero to thousands of concurrent executions, and pay-per-invocation pricing.

Core Capabilities

Function Handlers

// handler.ts — API Gateway Lambda (Node.js/TypeScript)
import { APIGatewayProxyHandlerV2 } from "aws-lambda";

export const handler: APIGatewayProxyHandlerV2 = async (event) => {
  const { httpMethod, pathParameters, body, queryStringParameters } = event;

  try {
    switch (httpMethod) {
      case "GET": {
        const id = pathParameters?.id;
        if (id) {
          const item = await db.get({ TableName: "users", Key: { id } });
          return { statusCode: 200, body: JSON.stringify(item.Item) };
        }
        const items = await db.scan({ TableName: "users" });
        return { statusCode: 200, body: JSON.stringify(items.Items) };
      }
      case "POST": {
        const data = JSON.parse(body || "{}");
        await db.put({ TableName: "users", Item: { id: uuid(), ...data } });
        return { statusCode: 201, body: JSON.stringify({ created: true }) };
      }
      default:
        return { statusCode: 405, body: "Method not allowed" };
    }
  } catch (error) {
    console.error(error);
    return { statusCode: 500, body: JSON.stringify({ error: "Internal error" }) };
  }
};

# handler.py — S3 event trigger (Python)
import json
import boto3
from PIL import Image
import io

s3 = boto3.client("s3")

def handler(event, context):
    """Process uploaded images: resize and create thumbnails.

    Triggered by S3 PutObject events on the uploads/ prefix.
    """
    for record in event["Records"]:
        bucket = record["s3"]["bucket"]["name"]
        key = record["s3"]["object"]["key"]

        # Download original
        response = s3.get_object(Bucket=bucket, Key=key)
        image = Image.open(io.BytesIO(response["Body"].read()))

        # Create thumbnail
        image.thumbnail((300, 300))
        buffer = io.BytesIO()
        image.save(buffer, format="JPEG", quality=85)
        buffer.seek(0)

        # Upload thumbnail
        thumb_key = key.replace("uploads/", "thumbnails/")
        s3.put_object(
            Bucket=bucket,
            Key=thumb_key,
            Body=buffer,
            ContentType="image/jpeg",
        )

    return {"statusCode": 200, "processed": len(event["Records"])}