AWS Lambda: Serverless Functions Complete Guide

AWS Lambda Guide

Serverless computing without managing servers.

Triggers

API Gateway, S3 events, SQS, DynamoDB streams, and scheduled events.

IAM Roles for Lambda

Lambda functions need the right IAM execution roles to interact with other AWS services:

• **AWSLambdaBasicExecutionRole** — grants permissions to write logs to CloudWatch. Required for virtually every function.
• **AWSLambdaVPCAccessExecutionRole** — allows the function to create and manage ENIs so it can run inside a VPC and reach private resources like RDS.
• **AWSLambdaDynamoDBExecutionRole** — grants read access to DynamoDB Streams so the function can process stream records as a trigger.

Lambda Free Tier

Lambda has a permanently free tier (not just the first 12 months): 1 million requests and 3.2 million seconds of compute time per month. For low-traffic APIs and automation tasks this often means zero cost.

API Gateway + Lambda vs EC2

For simple REST APIs, the API Gateway + Lambda combination is often a better choice than spinning up an EC2 instance. You get less infrastructure to manage, automatic scaling to zero and to peak, and a pure pay-per-request billing model — no idle cost.

Layers

Share code and dependencies across functions.

Cold Starts

Minimize cold starts with provisioned concurrency and SnapStart.

Cost Optimization

Right-size memory, use ARM, and optimize invocation patterns.

AWS Hosting Cost Comparison

When choosing where to run your workloads, pricing varies widely by service:

• **AWS Amplify** — roughly $8/month for 300 daily active users, scaling to about $66/month at 10,000 DAU. Great for full-stack web apps with auth, APIs, and hosting bundled together.
• **AWS Lightsail** — predictable monthly pricing starting at $3.50/month (512 MB RAM, 1 core) up to $160/month (32 GB RAM, 8 cores). Ideal when you want VPS simplicity with AWS integration.