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

  See also: Evolving Events Over Time

• 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...?.