Guides

Goal-oriented guides for building applications with Protean. Each guide covers a specific task with practical code examples.

If you haven't already, start with Hello, Protean! for a quick first taste, then work through the Tutorial to build a complete application from scratch. These guides go deeper into each topic and serve as a reference you'll return to as your application grows.

Choose Your Path

Protean supports three architectural approaches — DDD, CQRS, and Event Sourcing — each building on the one before it. Not sure which to use? Start with DDD and evolve later.

Compare pathways and choose

Browse by Topic

• Define Your Domain

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  Model your business concepts with aggregates, entities, value objects, and rich behavior.

  Set Up the Domain · Define Domain Elements · Add Rules and Behavior

• Change State

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  Process state changes through application services, commands, and command handlers. Persist and retrieve aggregates.

  Change State

• React to Changes

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  Respond to state changes with event handlers, projections, process managers, and subscribers.

  React to Changes

• Run in Production

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  Run the async processing server and integrate with FastAPI.

  Run the Server · FastAPI · Observability

  See also: Configuration · CLI · Adapters

• Test Your Application

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  Strategies for testing every layer of your application.

  Testing

How Do I...?

For the full task index, see How Do I...?.