AWS Lambda and Serverless

AWS Lambda lets you run code without provisioning or managing servers. You pay only for the compute time you consume — there is no charge when your code is not running. Lambda is the cornerstone of serverless computing on AWS.

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What Is Serverless?

Serverless doesn't mean there are no servers — it means you don't manage them. The cloud provider handles all the infrastructure: provisioning, scaling, patching, and availability.

Serverless Benefits

• No server management — focus entirely on your code
• Automatic scaling — from zero to thousands of concurrent executions
• Pay-per-use — charged only for actual compute time
• Built-in high availability — runs across multiple AZs automatically

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How Lambda Works

The Execution Model

1. You upload your code (a "function")
2. You configure a trigger (what causes the function to run)
3. When the trigger fires, Lambda runs your code in a managed environment
4. Lambda scales automatically — each trigger invocation gets its own execution environment

Supported Runtimes

Runtime	Languages
Node.js	JavaScript, TypeScript
Python	Python 3.x
Java	Java 8, 11, 17, 21
C#	.NET 6, 8
Go	Go 1.x
Ruby	Ruby 3.x
Custom	Any language via custom runtime

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Lambda Function Configuration

Setting	Description	Limits
Memory	128 MB to 10,240 MB	Proportionally allocates CPU
Timeout	Maximum execution time	1 second to 15 minutes
Environment variables	Key-value pairs for configuration	4 KB total
Concurrency	Number of simultaneous executions	1,000 default (can be increased)

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Common Triggers

Lambda functions can be triggered by many AWS services:

Trigger	Use Case
API Gateway	Build REST or HTTP APIs
S3	Process files when uploaded
DynamoDB Streams	React to database changes
SQS	Process messages from a queue
CloudWatch Events / EventBridge	Scheduled tasks (cron jobs)
SNS	React to notifications
Kinesis	Process streaming data

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Example: S3 Trigger

When a new image is uploaded to an S3 bucket, a Lambda function automatically creates a thumbnail: