What You Accomplished

You started with code on your laptop. Now you have an API running on AWS with a real URL. That’s a big step.

You learned:

What “the cloud” means (renting computers)
Three deployment models (local, VM, serverless)
How to build a Node.js API
How to adapt code for Lambda
How to deploy to AWS
How to use environment variables
How to check logs and debug
How pricing works

You built:

A working Notes API
Deployed it to Lambda
Connected it to API Gateway
Got a real URL anyone can call

Key Concepts Recap

Cloud Compute

The cloud = renting computers. You pay for what you use. No magic.

Three models:

Local: Your laptop (free, but not accessible)
VM: Virtual machine (pay per hour, full control)
Serverless: Functions (pay per request, no server management)

Serverless Benefits

For small projects:

Cheaper (pay per use)
Simpler (no server management)
Auto-scales
Easy deployment

Trade-offs:

Cold starts (first request can be slow)
Time limits (15 minutes max)
Less control

Request Flow

Client → API Gateway → Lambda → Your Code → Response

API Gateway: Receives HTTP, routes to Lambda.

Lambda: Runs your code on demand.

Your Code: Processes request, returns response.

Statelessness

Each request is independent. No shared memory. This is why we used in-memory storage (notes are lost on restart). For production, use a database.

Final Knowledge Check

Knowledge Check

This interactive quiz requires JavaScript to be enabled.

Question 1: What is the main difference between running code locally vs on Lambda?

A. Local code is faster
B. Local code runs continuously, Lambda runs on-demand (Correct)
C. Lambda code is written differently
D. There's no difference

Explanation: The key difference is that local code runs continuously (server always listening), while Lambda functions run only when invoked. This is why Lambda is 'serverless' - there's no server running 24/7.

Question 2: Why is serverless often cheaper for small projects compared to VMs?

A. Serverless is always free
B. You pay per request instead of per hour, so low traffic costs less (Correct)
C. VMs are more expensive to maintain
D. Serverless doesn't use any resources

Explanation: Serverless is cheaper for small projects because you pay per request. If your API gets called 100 times a day, you pay for 100 requests. With a VM, you pay $7.20/month even if you get 0 requests.

Question 3: What happens to in-memory data (like our notes array) when a Lambda function stops?

A. It's saved automatically
B. It's lost - each invocation is independent (Correct)
C. It's stored in CloudWatch
D. It persists between invocations

Explanation: Lambda functions are stateless. In-memory data is lost when the function stops. This is why we used in-memory storage for learning, but in production you'd use a database like DynamoDB or RDS.

Question 4: Where do console.log() statements from Lambda appear?

A. In your terminal
B. In CloudWatch Logs (Correct)
C. In API Gateway
D. They don't appear anywhere

Explanation: All console.log() output from Lambda functions is automatically sent to CloudWatch Logs. You can view it in the AWS Console under CloudWatch → Log groups.

Question 5: What is the main role of API Gateway in our architecture?

A. It runs our code
B. It receives HTTP requests and routes them to Lambda (Correct)
C. It stores our data
D. It provides the database

Explanation: API Gateway receives HTTP requests from the internet and routes them to Lambda functions. It also provides the public URL and handles things like CORS, authentication, and rate limiting.