Lambda

💡 Definition

AWS Lambda is a serverless compute service that lets you run code without provisioning or managing servers. You pay only for the compute time you consume.

🔑 Key Concepts

• Function: The code you upload to Lambda.
• Trigger: The event that causes the function to run (e.g., file upload to S3, HTTP request via API Gateway, record update in DynamoDB).
• Runtime: The language environment (Python, Node.js, Java, Go, etc.).
• Serverless: No OS access, no patching, automatic scaling.

⚙️ How it Works

1. Upload Code: Write your function logic.
2. Configure Trigger: Set up an event source (e.g., "When a file lands in S3 bucket X...").
3. Execution: When the event occurs, Lambda spins up, runs the code, and shuts down.
4. Scale: If 1,000 events happen at once, Lambda runs 1,000 copies of the function instantly.

🎯 Use Cases

• Real-time File Processing: Resize images immediately after upload to S3.
• Data Transformation: ETL jobs, filtering data streams.
• Backend Logic: Powering web/mobile apps via API Gateway.
• Automated Cron Jobs: Scheduled tasks using EventBridge.

💰 Pricing Model

• Requests: Charge per 1 million requests ($0.20).
• Duration: Charge for GB-seconds (how long the code runs * how much memory configured).
• Free Tier: 1 million free requests and 400,000 GB-seconds per month forever.

📝 Exam Tips (CLF-C02)

• Time Limit: Lambda functions have a maximum execution time (currently 15 minutes). Not for long-running processes (use EC2 or Fargate for that).
• Event-Driven: It runs in response to events.
• Cost-Effective: Zero cost when code is not running (unlike EC2 which charges when idle).

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See Also: * Fargate * API Gateway