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Clean Lambda Function
Lean Mean Clean Apps

Five templates, one search box. Everything in the docs is in here, including the bits we hoped you'd skim.

Try one of these

Results say which template they came from, so you won't end up reading about Lambda when you wanted GraphQL. Again.

Why it's built this way

Every template is a pile of opinions. Here are ours, so you can disagree with them on purpose rather than by accident.

Container image, not a zip

Section titled “Container image, not a zip”

A container image gives you the same artefact on your laptop, in CI and in AWS, and the base image includes the runtime emulator, so local testing is just docker run. It also gives you up to 10 GB to play with instead of 250 MB. The trade-off is a slightly slower first deploy while the image uploads.

Source generators everywhere

Section titled “Source generators everywhere”

Lambda bills you while your function wakes up, so the template avoids reflection where it can:

  • JSON uses the source-generated Lambda serializer.
  • Mediator generates its dispatch code at build time.
  • Mapperly generates mapping code at build time, and you can read exactly what it wrote.

As a bonus, MediatR and AutoMapper both moved to commercial licences in 2025, and this template didn’t have to care.

FluentValidation in a pipeline behaviour

Section titled “FluentValidation in a pipeline behaviour”

Validation runs once, in one place, before any handler. Handlers only ever see valid requests, which keeps them short and keeps tests honest.

SQLite in /tmp

Section titled “SQLite in /tmp”

The template needs a database that works in a container, on a laptop and in Lambda without any setup. SQLite in /tmp does that, with real caveats. It’s there to show the shape of Infrastructure, not to be your production database.

Infrastructure is internal

Section titled “Infrastructure is internal”

The one rule we bend is letting Presentation reference Infrastructure for dependency injection. Making every Infrastructure class internal means the compiler enforces the boundary instead of a code reviewer having a bad day.

Strict builds

Section titled “Strict builds”

Directory.Build.props turns on code style and the recommended analyzers for every project, and warnings fail the build. Directory.Packages.props keeps every package version in one place. It’s annoying for about a day and then you never want to go back.

Tests that don’t share

Section titled “Tests that don’t share”

Every test class gets its own in-memory SQLite database, built from the real migrations and the same fixed seed. Tests can run in any order, in parallel, forever, and still agree with each other.

Part of Lean Mean Clean Apps

Made by the Lean Mean Clean Apps team with Clean Architecture, strong coffee and a healthy disregard for pomp and ceremony. Not affiliated with Microsoft, AWS, Uncle Bob or anyone with a marketing budget.