Beginner guide to Serverless Cloud Applications on AWS

// Teaching excerpt for GET /products/{id}
export const handler = async (event) => {
  const id = event.pathParameters.id;
  const product = await getProductById(id);
  return {
    statusCode: product ? 200 : 404,
    body: JSON.stringify(product ?? { message: "Not found" }),
  };
};

{
  "productId": "bag-101",
  "name": "Northstar Daypack",
  "brand": "Northstar",
  "priceCents": 5900,
  "currency": "USD",
  "stock": 2,
  "imageKey": "products/bag-101.jpg"
}

// Inside our data helper; db is a DynamoDBDocumentClient.
const { Item } = await db.send(new GetCommand({
  TableName: process.env.PRODUCTS_TABLE,
  Key: { productId: id },
  ConsistentRead: true,
}));

POST /orders
Content-Type: application/json
Idempotency-Key: checkout-attempt-123

{"items":[{"productId":"bag-101","quantity":3}]}

// Inside an illustrative validator, after validating the request shape.
const product = await getProductById(item.productId);
if (!product) throw new Error("Product not found");
if (!Number.isInteger(item.quantity) || item.quantity < 1)
  throw new Error("Choose a positive whole-number quantity");
if (item.quantity > product.stock)
  throw new Error("Not enough stock");
const lineTotalCents = product.priceCents * item.quantity;

// accessToken comes from the completed sign-in flow.
await fetch(`${apiBase}/me/orders`, {
  headers: { Authorization: `Bearer ${accessToken}` },
});

// BrandIndex must exist with the keys and projected fields we need.
const page = await db.send(new QueryCommand({
  TableName: process.env.PRODUCTS_TABLE,
  IndexName: "BrandIndex",
  KeyConditionExpression: "#brand = :brand",
  ExpressionAttributeNames: { "#brand": "brand" },
  ExpressionAttributeValues: { ":brand": "Northstar" },
  Limit: 20,
}));