Day 20 - AWS Lambda

Cloud computing has evolved dramatically over the last decade.

The journey looked something like this:

Physical Servers
        ↓
Virtual Machines
        ↓
Containers
        ↓
Serverless Computing

One of the biggest innovations in cloud computing is AWS Lambda.

Instead of managing:

• Servers
• Operating Systems
• Patching
• Scaling
• Capacity Planning

You simply upload code and AWS runs it.

This is the foundation of Serverless Computing.

What is AWS Lambda?

AWS Lambda is a serverless compute service that allows you to run code without provisioning or managing servers.

You upload a function and AWS executes it whenever an event occurs.

Example:

User Uploads Image
        ↓
S3 Event Triggered
        ↓
Lambda Function Runs
        ↓
Image Processed

You only pay for execution time.

No execution means:

No Cost

Why AWS Introduced Lambda

Before Lambda, deploying applications looked like this:

Provision EC2
       ↓
Install Runtime
       ↓
Deploy Application
       ↓
Monitor Servers
       ↓
Scale Infrastructure
       ↓
Patch OS

Even small applications required infrastructure management.

AWS wanted developers to focus on:

Business Logic

Instead of:

Infrastructure Management

Thus Lambda was introduced in 2014.

What is Serverless?

Serverless does NOT mean servers don't exist.

Servers still exist.

AWS manages them for you.

Instead of:

You Manage Servers

Lambda provides:

AWS Manages Servers
You Manage Code

Example:

API Gateway
       ↓
Lambda
       ↓
DynamoDB

Benefits of AWS Lambda

1. No Server Management

No:

• EC2
• OS updates
• Capacity planning

2. Automatic Scaling

AWS automatically scales functions.

1 Request
      ↓
1 Lambda Instance

1000 Requests
      ↓
1000 Lambda Instances

3. Pay Per Use

You only pay for:

Requests
+
Execution Duration

4. Event Driven

Lambda reacts to events.

Examples:

• API requests
• S3 uploads
• SNS notifications
• SQS messages
• DynamoDB streams

5. High Availability

AWS automatically distributes Lambda execution across Availability Zones.

Supported Programming Languages

AWS Lambda supports multiple runtimes.

Python

Popular for:

• Automation
• AI/ML
• Data processing

Example:

import json

def lambda_handler(event, context):
    # TODO implement
    return {
        'statusCode': 200,
        'body': json.dumps('Hello from Lambda!')
    }

Node.js

Popular for:

• APIs
• Web applications

Java

Popular for:

• Enterprise workloads

.NET

Popular for:

• Microsoft environments

Go

Popular for:

• High performance
• Fast startup

Custom Runtime

Using Custom Runtime API, you can run:

• Rust
• PHP
• Other languages

Lambda Function Components

Every Lambda contains:

Function Code

Your business logic.

Runtime

Language execution environment.

Example:

Python 3.12
Node.js 20
Java 21

Handler

Entry point of Lambda.

Example:

lambda_handler(event, context)

AWS invokes this function.

Event

Input to the Lambda.

Example:

{
  "bucket": "images"
}

Context

Runtime information.

Contains:

• Request ID
• Timeout
• Memory

Lambda Execution Lifecycle

Request Arrives
        ↓
Environment Created
        ↓
Function Runs
        ↓
Response Returned

Understanding Cold Starts

One of the most important Lambda concepts.

Cold Start

When Lambda has no running execution environment:

Request Arrives
       ↓
Create Environment
       ↓
Load Runtime
       ↓
Execute Function

Extra startup time occurs.

Warm Start

If environment already exists:

Request Arrives
       ↓
Execute Function Immediately

Faster response.

What is Concurrency?

Concurrency means:

How Many Functions
Can Run Simultaneously

Example:

100 Requests
       ↓
100 Concurrent Executions

Reserved Concurrency

Reserve capacity for critical workloads.

Example:

Payment Function
Reserved = 100

Always guaranteed.

Provisioned Concurrency

Used to eliminate cold starts.

AWS keeps execution environments warm.

Useful for:

• APIs
• User-facing workloads

What is Lambda Scaling?

Lambda automatically scales horizontally.

1 Request
       ↓
1 Environment

10000 Requests
       ↓
10000 Environments

No manual scaling required.

What is a Lambda Layer?

One of the most important Lambda concepts.

Lambda Layers allow sharing code across multiple functions.

Without Layers:

Function A
 └─ boto3

Function B
 └─ boto3

Function C
 └─ boto3

Duplication occurs.

With Layers

Layer
 └─ boto3

Function A
Function B
Function C

All functions share the same dependency.

Why Lambda Layers Matter

Benefits:

• Smaller deployment packages
• Reusability
• Easier maintenance
• Faster deployments

Common Layer Use Cases

Python Libraries

numpy
pandas
requests

Monitoring Agents

Datadog
New Relic
OpenTelemetry

Lambda Storage Options

Temporary Storage

/tmp

Default:

512 MB

Can be increased.

Amazon S3

Persistent object storage.

Used for:

• Files
• Images
• Backups

Amazon EFS

Network file system for Lambda.

Useful for:

• Shared storage
• Large datasets

Event Sources for Lambda

API Gateway

User Request
      ↓
API Gateway
      ↓
Lambda

Most common pattern.

Amazon S3

File Uploaded
      ↓
Lambda Triggered

Lambda and VPC

By default:

Lambda
     ↓
AWS Managed Network

For private resources:

Lambda
     ↓
VPC
     ↓
RDS

Lambda can connect to:

• RDS
• ElastiCache
• Private APIs

Lambda with RDS

Common architecture:

API Gateway
      ↓
Lambda
      ↓
Aurora MySQL

Challenges:

• Connection management
• Database scaling

Solution:

RDS Proxy

Lambda Monitoring

CloudWatch Logs

Automatically captures:

• stdout
• stderr
• application logs

CloudWatch Metrics

Monitor:

• Invocations
• Duration
• Errors
• Throttles
• Concurrent executions

AWS X-Ray

Distributed tracing for Lambda applications.

Useful for:

• Performance analysis
• Bottleneck detection

Lambda Security

IAM Roles

Lambda should never use hardcoded credentials.

Use:

IAM Execution Role

Secrets Manager

Store:

• Database passwords
• API keys
• Tokens

KMS Encryption

Encrypt:

• Environment variables
• Data

Lambda Limits

Some important limits:

Real-World Lambda Use Cases

Image Processing

S3 Upload
      ↓
Lambda
      ↓
Resize Image

Serverless APIs

API Gateway
      ↓
Lambda
      ↓
DynamoDB

Log Processing

CloudWatch Logs
       ↓
Lambda
       ↓
Elasticsearch/OpenSearch

Scheduled Jobs

EventBridge
      ↓
Lambda
      ↓
Daily Report

Production Best Practices

Keep Functions Small

One function = one responsibility.

Use Layers

Avoid dependency duplication.

Enable Monitoring

Use:

• CloudWatch
• X-Ray

Use Provisioned Concurrency

For latency-sensitive APIs.

Use RDS Proxy

For database-heavy workloads.

Secure Secrets

Use:

• Secrets Manager
• Parameter Store

Never hardcode credentials.

Final Thoughts

AWS Lambda transformed cloud computing by allowing developers to focus entirely on code.

Instead of managing:

Servers
Operating Systems
Scaling
Patching

you simply write functions and AWS handles the infrastructure.

Lambda is ideal for:

• APIs
• Event-driven applications
• Automation
• Data processing
• Serverless architectures

Understanding concepts like:

• Layers
• Cold Starts
• Concurrency
• Provisioned Concurrency
• Event Sources
• RDS Proxy

is essential for designing production-grade serverless applications.

For modern cloud engineers, AWS Lambda is no longer optional—it is one of the most important services in the AWS ecosystem.