What are AWS Lambda and Serverless?

Question

Accepted Answer

**AWS Lambda** — serverless compute: pay only for execution time.

**Example (Node.js):**
```javascript
exports.handler = async (event) => {
  return {
    statusCode: 200,
    body: JSON.stringify({ message: "Hello from Lambda!" }),
  };
};
```

**CLI:**
```bash
aws lambda create-function \
  --function-name my-function \
  --runtime nodejs18.x \
  --handler index.handler \
  --role arn:aws:iam::xxx:role/lambda-role \
  --zip-file fileb://function.zip

aws lambda invoke --function-name my-function output.json
```

**Use cases:** API Gateway + Lambda, S3 → Lambda, SQS → Lambda, Cron.

**Limits:** 15 min timeout, 10GB memory, cold start.

**Serverless Framework:**
```yaml
service: my-api
provider:
  name: aws
  runtime: nodejs18.x
functions:
  hello:
    handler: handler.hello
    events:
      - http:
          path: /hello
          method: get
```

DevOps: What are AWS Lambda and Serverless?