APIs: Why Rust’s Axum Leads Over Python’s FastAPI

Rust's Cuddly Ferris vs Python's Pythons

In a real-world example, the difference between running a FastAPI container versus an Axum container is astonishing. The amount of memory and CPU usage for an API container that performs a series of complicated equations is astounding enough that future use cases of Python have to be seriously considered against why they should be used over Rust.

Let’s break down the actual results:

  • FastAPI (Python)
    • CPU usage: ~13% of one core
    • Memory usage: ~55MB
  • Axum (Rust)
    • CPU usage: ~3% of one core
    • Memory usage: ~3.5MB

This isn’t a minor difference — this is an entire order of magnitude in resource savings. And that’s without making any extreme optimization effort on the Rust side. The Axum container wasn’t stripped down or custom-tuned. It was just… efficient, out of the box.

But why is this happening?

Python is an interpreted language with a significant runtime overhead. Even with tools like uvicorn or gunicorn, Python apps like FastAPI rely heavily on dynamic typing and abstraction layers that carry performance costs.

Rust, on the other hand, compiles down to bare metal. The Axum framework is minimal, async-first, and designed with zero-cost abstractions in mind. In practice, this means it doesn’t do more than it has to.

Does this matter?

Yes. Especially in cloud environments.

When you’re scaling microservices or deploying to memory-constrained environments (think: edge compute, IoT, or lean VPS setups), cutting memory usage by 90% and CPU usage by 75% translates directly into cost savings and faster response times.

It’s not just academic anymore. This is real-world measurable efficiency.

Should everyone ditch FastAPI?

Not necessarily. Python has a fantastic developer experience. The learning curve is shallow and the ecosystem is mature.

But if you’re building something where performance and predictability matter — Axum might just be the better choice. Especially when your workload involves repetitive computations, API endpoints under load, or you’re planning to scale horizontally.

TL;DR

If you’re building an API that needs to scale and perform, Rust’s Axum framework offers serious benefits over Python’s FastAPI. Lower memory usage. Lower CPU usage. And once you’ve got your feet wet in Rust, it’s hard to look back.