Layered Rails Architecture

Audience: Rails developers working on applications that have outgrown single-file patterns. Goal: Know which layer code belongs in, when to extract, and which existing skill handles the implementation.

Four-Layer Architecture

Presentation  →  Application  →  Domain  →  Infrastructure
(HTTP/UI)        (Orchestration)  (Business)   (Persistence/APIs)

Core rule: Lower layers MUST NOT depend on higher layers. Data flows top-to-bottom only.

Layer Responsibilities