Deployment Overview

We’ll do this in steps:

1. Package your code
2. Create a Lambda function
3. Upload the code
4. Create an API Gateway
5. Connect them
6. Test the URL

Let’s go.

Step 1: Package Your Code

Lambda needs your code in a zip file. Create the zip:

zip -r function.zip lambda-handler.js

Note: If you used Express with aws-serverless-express, include node_modules:

zip -r function.zip lambda-handler.js node_modules/

But for our simple handler, we don’t need any dependencies, so just the handler file is enough.

Step 2: Choose a Region

Log into AWS Console and pick a region. We’ll use us-east-1 (N. Virginia) in examples, but pick one close to you.

Why regions matter: Lower latency for your users, and some services are region-specific.

Step 3: Create Lambda Function

1. Go to AWS Console → Lambda
2. Click “Create function”
3. Choose “Author from scratch”
4. Fill in:
   • Function name: notes-api
   • Runtime: Node.js 18.x (or latest)
   • Architecture: x86_64
5. Click “Create function”

You’ll see the function configuration page.

Step 4: Upload Your Code

1. Scroll to “Code source”
2. Click “Upload from” → “.zip file”
3. Select your function.zip file
4. Click “Save”

AWS will upload and extract your code.

Step 5: Set the Handler

The handler tells Lambda which function to call.

1. In “Code source”, find “Runtime settings”
2. Click “Edit”
3. Set Handler to: lambda-handler.handler
   • This means: file is lambda-handler.js, function is handler
4. Click “Save”

Step 6: Test Lambda (Optional but Recommended)

Before connecting to API Gateway, test Lambda directly:

1. Click “Test” tab
2. Click “Create new test event”
3. Name it “test-get-notes”
4. Use this JSON:

{
  "path": "/notes",
  "httpMethod": "GET",
  "headers": {},
  "body": null
}

5. Click “Save”
6. Click “Test”

You should see:

• Status: “Succeeded”
• Response: Your notes JSON

If you see an error, check:

• Handler name is correct
• Code uploaded successfully
• JSON syntax is valid

Step 7: Create API Gateway

Now create the HTTP endpoint:

1. Go to AWS Console → API Gateway
2. Click “Create API”
3. Choose “HTTP API” (not REST API - HTTP is simpler)
4. Click “Add integration”
5. Select:
   • Integration type: Lambda
   • Lambda function: notes-api (the one you created)
6. Click “Next”
7. Configure routes:
   • Method: GET
   • Resource path: /notes
   • Click “Add another route”
   • Method: GET
   • Resource path: /health
   • Click “Add another route”
   • Method: POST
   • Resource path: /notes
8. Click “Next”
9. Review and click “Create”

Step 8: Deploy the API

1. You’ll see your API dashboard
2. Click “Deploy”
3. Choose stage: prod (or create a new one)
4. Click “Deploy”

You’ll get a URL like:

https://abc123xyz.execute-api.us-east-1.amazonaws.com

This is your API endpoint!

Step 9: Test the Real URL

Open a terminal and test:

curl https://abc123xyz.execute-api.us-east-1.amazonaws.com/health

You should see:

{"status":"ok","timestamp":"2025-12-02T10:00:00.000Z"}

Test notes:

curl https://abc123xyz.execute-api.us-east-1.amazonaws.com/notes

Test POST:

curl -X POST https://abc123xyz.execute-api.us-east-1.amazonaws.com/notes \
  -H "Content-Type: application/json" \
  -d '{"text":"Test from cloud"}'

It works! Your API is live on the internet.

Understanding IAM

What is IAM? Identity and Access Management. It’s how AWS says “who can do what.”

For Lambda:

• Lambda needs permission to run (it gets this automatically)
• API Gateway needs permission to call Lambda (we set this up when creating the integration)

Least privilege: Give only the permissions needed. For this tutorial, the defaults are fine.

You don’t need to configure IAM manually - API Gateway sets it up when you create the integration.

Understanding Cold Starts

What is a cold start? The first request after inactivity can be slow (1-3 seconds). Lambda needs to start the function.

Why it happens: Lambda stops your function when not used. Starting it takes time.

How to reduce:

• Use Provisioned Concurrency (costs money)
• Keep functions warm with scheduled pings
• For most APIs, cold starts are fine (users don’t notice 1-2 seconds)

For this tutorial: Don’t worry about it. Your API will work fine.

Request Flow Visualization

Troubleshooting

“Internal server error” (500):

• Check Lambda logs (CloudWatch)
• Verify handler name is correct
• Check code for syntax errors

“Resource not found” (404):

• Check route path matches (/notes not /note)
• Verify API Gateway is deployed
• Check stage name in URL

“Timeout”:

• Lambda has a default 3-second timeout
• Increase it in Lambda settings if needed
• Check if code has infinite loops

“Permission denied”:

• API Gateway needs permission to invoke Lambda
• Re-check the integration settings

Key Takeaways

Before moving on:

1. Package code as zip - Lambda needs code packaged
2. Handler name matters - filename.functionName
3. API Gateway creates the URL - It’s your public endpoint
4. Test before deploying - Use Lambda test events first
5. IAM handles permissions - Usually automatic, but good to understand

What’s Next?

In the next page, we’ll add environment variables, check logs, and learn basic troubleshooting. This helps you debug issues in production.