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Lambda (AWS Serverless) vs FastAPI

Lambda (AWS Serverless) logo

Lambda (AWS Serverless)

Software

Run code without thinking about servers

From
Free
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

  • Each has a real cost: Lambda (AWS Serverless) billed on two axes at once, $0.20 per million requests plus $0.0000166667 per GB-second of duration, so memory settings change the bill as much as traffic does; 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 Lambda (AWS Serverless) and FastAPI actually diverge.

Attributes where Lambda (AWS Serverless) and FastAPI differ
AttributeLambda (AWS Serverless)FastAPI
Pricing modelusage-basedopen-source
PlatformsWeb, ApiWeb
Founded2014Unknown

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Unknown).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Lambda (AWS Serverless)

  • Function-as-a-Service
  • Event-driven execution
  • Auto-scaling
  • Pay-per-use
  • Multiple languages
  • Concurrency limits
  • Dead Letter Queues
  • Environment variables

Only in FastAPI

Nothing recorded that Lambda (AWS Serverless) does not also cover.

What people use each for

The jobs each tool is most often brought in to do.

Lambda (AWS Serverless)

  • Event-driven functions without managing serversnot FastAPI
  • API backends behind API Gatewaynot FastAPI
  • Processing S3, DynamoDB, SQS and Kinesis eventsnot FastAPI
  • Scheduled jobs without a always-on instancenot FastAPI
  • Edge compute through Lambda@Edgenot FastAPI

FastAPI

No use cases recorded yet. See the FastAPI review.

Where each one falls short

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

Lambda (AWS Serverless)

  • Billed on two axes at once, $0.20 per million requests plus $0.0000166667 per GB-second of duration, so memory settings change the bill as much as traffic does
  • Provisioned concurrency, used to avoid cold starts, is charged separately at $0.0000041667 per GB-second whether or not the function runs
  • Ephemeral storage beyond the included 512 MB is metered
  • Lambda@Edge costs $0.60 per million requests, three times the standard request rate
  • VPC use and cross-region data transfer carry EC2 charges on top

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

Lambda (AWS Serverless)

Free
  • Free TierFree
    • 1M free requests/month
    • 400,000 GB-seconds/month
    • Always free

FastAPI

Free

No published plan breakdown. See the FastAPI review.

Which should you pick?

Choose Lambda (AWS Serverless) if

  • You need function-as-a-service.
  • You want to start without paying.
  • You work on Web, Api.
  • You also want event-driven execution.
Lambda (AWS Serverless) review

Choose FastAPI if

  • You want to start without paying.
FastAPI review

Questions people ask

Is Lambda (AWS Serverless) or FastAPI better?
Neither clearly leads. Lambda (AWS Serverless) starts at Free and FastAPI at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Lambda (AWS Serverless) or FastAPI?
Lambda (AWS Serverless) starts at Free and FastAPI at Free.
Does Lambda (AWS Serverless) or FastAPI run on more platforms?
Lambda (AWS Serverless) runs on Web, Api. FastAPI runs on Web.
Can I use Lambda (AWS Serverless) for free?
Both have a free tier, so you can try either at no cost before committing.
What is Lambda (AWS Serverless) best used for?
Lambda (AWS Serverless) is most often used for event-driven functions without managing servers, api backends behind api gateway, processing s3, dynamodb, sqs and kinesis events, scheduled jobs without a always-on instance. Of those, event-driven functions without managing servers and api backends behind api gateway are not what FastAPI is typically brought in for.
What can Lambda (AWS Serverless) do that FastAPI cannot?
Lambda (AWS Serverless) covers Function-as-a-Service, Event-driven execution, Auto-scaling, Pay-per-use.
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