Lambda Demo

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Create a Lambda function (step-by-step)

1. Open the AWS Console, search for Lambda, and choose Create a function.
2. Choose Author from scratch to start with a blank function (you can also use a blueprint or container image).
3. Enter a function name (for example, firstFunction) and choose a runtime (Node.js, Python, Java, etc.). Examples below use Node.js with an ESM-style handler.
4. For execution role, accept Create a new role with basic Lambda permissions so the function can write logs to CloudWatch. Leave advanced settings (VPC, etc.) unchecked for this demo.
5. Click Create function.

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Lambda function configuration and destinations

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Default handler (Node.js ESM)

export const handler = async (event) => {
  // Example response returned to the caller (such as API Gateway)
  const response = {
    statusCode: 200,
    body: JSON.stringify('Hello from Lambda!')
  };
  return response;
};

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Triggers — when your function runs

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Test your function without a trigger

{
  "key1": "value1",
  "key2": "value2",
  "key3": "value3"
}

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Reading data from the event

{
  "products": "TV"
}

export const handler = async (event) => {
  const products = event.products;
  const response = {
    statusCode: 200,
    body: JSON.stringify("Product: " + products),
  };
  return response;
};

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Deploying an API Gateway trigger

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Using third‑party Node.js libraries (example: bcryptjs)

npm install bcryptjs

import bcrypt from "bcryptjs";

export const handler = async (event) => {
  const numSaltRounds = 8;
  const password = event.password || "";

  // Using synchronous API for simplicity in the console editor
  const hashedPassword = bcrypt.hashSync(password, numSaltRounds);

  const response = {
    statusCode: 200,
    body: JSON.stringify("Hashed Password: " + hashedPassword),
  };
  return response;
};

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Why you might see “Cannot find package”

{
  "errorType": "Error",
  "errorMessage": "Cannot find package 'bcryptjs' imported from /var/task/index.mjs"
}

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Bundling code and node_modules in a ZIP

1. On your machine create a project folder containing:
   • your handler file (e.g., index.mjs)
   • package.json (optional)
   • the node_modules folder created by npm install
2. Compress those items into a ZIP file (for example, hashLambda.zip).
3. In the Lambda console choose Upload from → .zip file, upload the ZIP, and deploy.

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Using Lambda Layers to share libraries

1. Create a folder named nodejs and copy your node_modules into it so the ZIP root contains nodejs/node_modules/....
2. Zip the nodejs folder (for example, hash-layer.zip).
3. In the Lambda console go to Layers → Create layer, upload the ZIP, set compatible runtimes (e.g., nodejs18.x), and create the Layer.
4. In your function’s configuration, add the Layer (choose the desired version). The function can then import packages from the Layer at runtime.

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Monitoring, metrics, and logs

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Summary

• Create a Lambda with Author from scratch and choose the correct runtime.
• Use triggers (API Gateway, S3, SNS, SQS, EventBridge) to invoke Lambda.
• Test functions in the console with JSON test events.
• Include third‑party Node.js packages by zipping node_modules with the function or by using a Lambda Layer.
• Monitor functions with the Lambda console and CloudWatch Logs/Metrics.

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Links and references

• AWS Lambda Developer Guide
• API Gateway documentation
• bcryptjs on npm
• AWS Lambda Layers documentation
• CloudWatch Logs documentation