AWS Lambda vs EC2: Key Differences and When to Use Each

AWS Lambda is a serverless compute service that runs code in response to events without managing servers, while EC2 provides virtual servers where you control the operating system and software. Lambda automatically scales with demand and charges per execution, whereas EC2 requires manual scaling and charges per running instance hour.

Quick Comparison

This table summarizes the main differences between AWS Lambda and EC2.

Factor	AWS Lambda	AWS EC2
Compute Model	Serverless, event-driven	Virtual servers (IaaS)
Server Management	No server management	Full server control
Scaling	Automatic scaling per request	Manual or auto scaling groups
Billing	Pay per execution time	Pay per running instance hour
Use Case	Short tasks, event triggers	Long-running apps, custom OS
Startup Time	Milliseconds	Minutes

Key Differences

AWS Lambda runs your code only when triggered by events like file uploads or API calls. You don't manage servers or operating systems, which means less setup and maintenance. Lambda automatically scales to handle any number of requests instantly.

EC2 gives you full control over virtual servers. You choose the operating system, install software, and manage security. You must handle scaling by adding or removing instances yourself or using auto scaling groups.

Billing also differs: Lambda charges based on the number of requests and execution duration, making it cost-effective for intermittent workloads. EC2 charges for every hour an instance runs, which suits steady, long-running applications.

Code Comparison

Here is a simple example of a function that returns a greeting message in AWS Lambda using Python.

python

def lambda_handler(event, context):
    name = event.get('name', 'World')
    return {
        'statusCode': 200,
        'body': f'Hello, {name}!'
    }

Output

{"statusCode": 200, "body": "Hello, World!"}

EC2 Equivalent

On EC2, you would write a simple Python web server using Flask to handle requests and return greetings.

python

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/greet')
def greet():
    name = request.args.get('name', 'World')
    return jsonify({'message': f'Hello, {name}!'})

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=80)

Output

{"message": "Hello, World!"}

When to Use Which

Choose AWS Lambda when you want to run short, event-driven tasks without managing servers, especially if your workload is unpredictable or spiky. Lambda is great for APIs, data processing, and automation.

Choose EC2 when you need full control over the server environment, run long-lasting applications, or require custom software and operating systems. EC2 suits traditional web servers, databases, and applications needing persistent compute resources.

Key Takeaways

AWS Lambda is serverless and event-driven, requiring no server management.

EC2 provides full control over virtual servers but needs manual scaling and management.

Lambda charges per execution, ideal for short, bursty workloads; EC2 charges per running hour, better for steady use.

Use Lambda for quick, stateless functions triggered by events.

Use EC2 for long-running, customizable server applications.