Fargate vs Lambda: A Simple Guide to Choosing

A simple, accessible guide to understanding the difference between Fargate and Lambda, and choosing the right service for your project.

1. Fargate – “Run my full application”

What is it for?

Fargate is for running full applications (like a website, an API, a backend, etc.) in Docker containers, with no servers to manage.

When do you use it?

• When you have a larger or more structured project (e.g., Node.js, Python Flask, Django, etc.)
• When your app runs all the time or for long periods (e.g., a website, a background service)

Concrete example:

You have a Node.js application with a database, routes, and complete logic.
You put it in a Docker container, and you tell Fargate:

“Here, run my app 24/7 and take care of everything it needs.”

2. Lambda – “Just run a small piece of code on demand”

What is it for?

Lambda is for running a short function (like a mini task), only when needed. No container, no server.

When do you use it?

• When you just want to respond to an event (e.g., an API call, an image arriving in S3…)
• When your code is short and only runs for a few seconds at a time
• When you want to pay only for what you use

Concrete example:

Someone submits a form on your site. You want to automatically send an email.
You write a function that does that (in Python or Node), and you tell Lambda:

“Run this code only when the form is submitted.”

Ultra-simple comparison:

Feature	Fargate	Lambda
App type	Full application	Short function / single task
Deployment format	Docker container	Code (.js, .py file, etc.)
Starts when?	Always online or on demand	Only when something happens
Execution time	Long-running (minutes, hours, days)	Short-running (a few seconds, max 15 min)
Typical use	Web APIs, backends, websites, microservices	One-off tasks, automation, lightweight APIs
Level of control	Medium (you manage your container)	Very low (you only manage the code)
Billing	Per minute of container runtime	Per invocation and exact execution time

An example to help you visualize:

You want to build an e-commerce site:

• You have a full backend with cart, login, and payment → Fargate
• When someone makes a purchase, you want to email them a receipt → Lambda

Simple summary:

• Fargate: you have an application to host.
• Lambda: you have a function to run when something happens.

Common Use Cases

With Fargate

• Full website
• Backend API
• Data processing service
• Application with a database

With Lambda

• Sending emails
• Image processing
• Responding to form submissions
• Scheduled tasks

Best Practices

For Fargate

• Optimize the container size
• Configure auto-scaling
• Monitor costs

For Lambda

• Keep functions short
• Optimize execution time
• Handle errors

Conclusion

Choosing between Fargate and Lambda depends on what you want to do:

• A full application? → Fargate
• A simple function? → Lambda

Additional Resources

• AWS Fargate Documentation
• AWS Lambda Documentation
• AWS Free Tier
• AWS Training