Layer

How to organize complex systems through layers and hierarchies. Breaking down big problems into manageable pieces.

Why Layers?

Layers help us manage complexity by creating clear boundaries:

• Each layer has one job
• Layers talk to each other through simple contracts
• Changes in one layer don't break others
• Systems can grow without becoming chaotic

Common Layers

• ui — What users see and interact with
• business — Core rules and workflows
• data — Storage and retrieval
• platform — Infrastructure and services

Cross-System Concerns

• auth — Who can do what
• logging — What's happening in the system
• api — How systems talk to each other
• cache — Making things faster

Design Principles

• Keep related things together
• Depend on abstractions, not concrete things
• Make interfaces small and focused
• Isolate changes within layers

Communication Patterns

• top-down — Commands flow from UI to data
• bottom-up — Events bubble up from data to UI
• sideways — Services talk to each other
• shortcuts — Direct paths for performance

In Practice

• Organize code into folders by layer
• Use consistent naming across projects
• Test each layer independently
• Test interactions between layers

Related

Works with entry patterns, value measurements, and std conventions.