Lambda vs Fargate: AWS Cost Comparison

A simple guide to understanding the costs of AWS Lambda and Fargate, and choosing the most cost-effective option for your needs.

🟦 AWS Lambda – Cheaper if you’re doing small things

• You pay per invocation (every time your code runs).
• You also pay for execution time (e.g., 100 ms, 500 ms…).

Example:
If your code runs for 1 second, 100 times a day → you pay almost nothing.

So Lambda is a great fit if:

• You have small functions
• You don’t need an app that runs all the time
• You want to optimize costs

🟧 AWS Fargate – More expensive but built for full applications

• You pay per second your container runs (CPU + RAM).
• Even if nobody is using your app, you pay as long as it’s running (unless you shut it down).

Example:
You run a container 24/7 with 0.5 vCPU and 1 GB of RAM → about $10 to $15/month minimum.

So Fargate is better if:

• Your app runs all the time
• You need a real API or a full website
• You have more business logic than a simple function

Direct Cost Comparison (approximate)

Service	Typical use	Estimated cost
Lambda	Short function (e.g., sending an email, resizing an image)	A few cents to $1/month
Fargate	Web application (e.g., Node.js + API) running 24/7	$10–$30/month per container

The Very Simple Summary:

You want to save as much as possible	→ Lambda (if your app can work as functions)
You want a full app that keeps running	→ Fargate (more expensive, but more powerful)

Cost Breakdown

AWS Lambda

• Per-request billing: ~$0.0000002 per request
• Duration billing: ~$0.00001667 per GB-second
• Free: 1 million requests/month
• Free: 400,000 GB-seconds/month

AWS Fargate

• Per-vCPU billing: ~$0.04048/hour
• Per-GB RAM billing: ~$0.00445/hour
• Recommended minimum: 0.5 vCPU + 1 GB RAM
• No free tier

Real-World Cost Examples

Lambda Example

• Email-sending function
  • 100 invocations/day
  • 1 second of execution
  • Monthly cost: ~$0.01

Fargate Example

• Node.js API
  • Runs 24/7
  • 0.5 vCPU + 1 GB RAM
  • Monthly cost: ~$15

Cost Optimization

For Lambda

• Optimize execution time
• Reduce allocated memory
• Use the free tier
• Group functions together

For Fargate

• Right-size your containers
• Use auto scaling
• Stop unused containers
• Choose the right region

Conclusion

The choice between Lambda and Fargate depends on your needs and your budget:

• Lambda: ideal for small functions and minimal costs
• Fargate: better for full applications that run continuously

Additional Resources

• AWS Lambda Pricing
• AWS Fargate Pricing
• AWS Cost Explorer
• AWS Pricing Calculator
• AWS Free Tier