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Azure Functions vs FastAPI

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Azure Functions

Software

Event-driven serverless compute on Azure

From
On request
Rated
-
Full reviewWebsite
F

FastAPI

Software

A modern, fast, high-performance web framework for building APIs with Python

From
Free
Rated
-
Full reviewWebsite

The short version

  • Only FastAPI has a free tier, so it costs nothing to try first.
  • Each has a real cost: Azure Functions consumption plan free grant is capped at 1 million executions and 400,000 GB-seconds of resource consumption per month per subscription, billed per GB-second beyond that; FastAPI licensed under the MIT License per fastapi.tiangolo.com; as open source software it has no paid tier or vendor price to compare

Where they differ

Only the attributes on which Azure Functions and FastAPI actually diverge.

Attributes where Azure Functions and FastAPI differ
AttributeAzure FunctionsFastAPI
Starting priceOn requestFree
Pricing modelsubscriptionopen-source
Free tierNoYes

Identical on both: platforms (Web), user rating (Not yet rated), category (Unknown).

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Azure Functions

  • Consumption plan free grant is capped at 1 million executions and 400,000 GB-seconds of resource consumption per month per subscription, billed per GB-second beyond that
  • The newer Flex Consumption plan's free grant is smaller still, at 250,000 executions and 100,000 GB-seconds per month
  • Premium plan avoids per-execution charges but bills continuously for allocated core seconds and memory regardless of invocation volume
  • Memory is rounded up to the nearest 128 MB and execution time to the nearest 1 ms for billing, so small overages round upward

FastAPI

  • Licensed under the MIT License per fastapi.tiangolo.com; as open source software it has no paid tier or vendor price to compare
  • FastAPI depends entirely on Starlette for its web layer and Pydantic for validation, per its own documentation, so it is not a standalone framework and inherits both dependencies' constraints

Pricing, plan by plan

Azure Functions

On request

No published plan breakdown. See the Azure Functions review.

FastAPI

Free

No published plan breakdown. See the FastAPI review.

Which should you pick?

Choose Azure Functions if

Nothing in the data separates Azure Functions from FastAPI on the points above - pick on price and on how each one feels to use.

Azure Functions review

Choose FastAPI if

  • You want to start without paying.
FastAPI review

Questions people ask

Is Azure Functions or FastAPI better?
Neither clearly leads. Azure Functions starts at On request and FastAPI at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Azure Functions or FastAPI?
FastAPI has a free tier; the other does not. Paid plans start at On request for Azure Functions and Free for FastAPI.
Does Azure Functions or FastAPI run on more platforms?
Both run on Web, so platform support will not decide this one for you.
Can I use FastAPI for free?
Yes. FastAPI has a free tier, so you can try it without paying. Azure Functions starts at On request.
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