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What I do

I provide guidance on building serverless applications using Functions-as-a-Service (FaaS) and managed services.

When to use me

Load this skill when:

• Event-driven workloads
• Variable/unpredictable traffic patterns
• Want to minimize operational overhead
• Pay-per-use cost model preferred
• Rapid iteration and deployment
• Don't need long-running processes

Core Principles

1. Stateless Functions

Functions don't maintain state between invocations.

2. Event-Driven

Functions triggered by events (HTTP, queue, schedule, etc.).

3. Managed Infrastructure

No server management - cloud provider handles scaling.

4. Pay Per Execution

Only pay for actual function execution time.

Function Structure

// AWS Lambda handler
export const handler = async (event: APIGatewayEvent) => {
  const userId = event.pathParameters?.id;
  
  const user = await dynamodb.get({
    TableName: 'Users',
    Key: { id: userId },
  });
  
  return {
    statusCode: 200,
    body: JSON.stringify(user),
  };
};

Event Sources

HTTP (API Gateway)

// GET /users/{id}
export const getUser = async (event: APIGatewayEvent) => {
  // Handle GET request
};

// POST /users
export const createUser = async (event: APIGatewayEvent) => {
  // Handle POST request
};

Queue (SQS, EventBridge)

export const processOrder = async (event: SQSEvent) => {
  for (const record of event.Records) {
    const order = JSON.parse(record.body);
    await processOrderLogic(order);
  }
};

Schedule (Cron)

// Run every hour
export const cleanupOldRecords = async () => {
  const cutoffDate = new Date();
  cutoffDate.setHours(cutoffDate.getHours() - 24);
  
  await dynamodb.delete({
    TableName: 'TempRecords',
    Key: { createdAt: { $lt: cutoffDate } },
  });
};

Advantages

1. No Server Management: Focus on code, not infrastructure
2. Auto-Scaling: Automatic scaling to demand
3. Cost Efficient: Pay only for execution time
4. Fast Deployment: Deploy functions independently
5. Built-in HA: High availability by default

Challenges

1. Cold Starts: Initial invocation latency
2. Execution Limits: Timeout constraints (15 min AWS Lambda)
3. Vendor Lock-in: Platform-specific code
4. Debugging: Harder to debug distributed functions
5. State Management: No local state between invocations

Best Practices

1. Keep functions small: Single responsibility
2. Minimize cold starts: Keep dependencies minimal
3. Use managed services: DynamoDB, S3, SQS instead of self-hosted
4. Handle errors gracefully: Implement retries and dead letter queues
5. Monitor everything: CloudWatch, distributed tracing
6. Optimize bundle size: Tree-shake dependencies

Example Stack (AWS)

API Gateway → Lambda → DynamoDB
                    → S3
                    → SQS → Lambda → External API

Infrastructure as Code

# serverless.yml
service: user-service

provider:
  name: aws
  runtime: nodejs18.x

functions:
  getUser:
    handler: src/handlers/getUser.handler
    events:
      - http:
          path: users/{id}
          method: get
  
  createUser:
    handler: src/handlers/createUser.handler
    events:
      - http:
          path: users
          method: post

resources:
  Resources:
    UsersTable:
      Type: AWS::DynamoDB::Table
      Properties:
        TableName: Users
        BillingMode: PAY_PER_REQUEST

References

• AWS Lambda documentation
• Serverless Framework
• AWS SAM (Serverless Application Model)