phoenix

name	phoenix
description	Core Phoenix framework patterns — context boundaries, LiveView, Ecto, and application architecture. Use when building, reviewing, or refactoring Phoenix applications.

Phoenix Two-Sided Split

The most important pattern in Phoenix:

Contexts	Web layer
Business logic — database queries, validations, business rules	Web interface — routes, controllers, LiveViews, templates, components
No HTML, no HTTP, no web concerns	Calls into contexts but never contains business logic itself

The web layer asks contexts for data. Contexts know nothing about the web.

The Violation

When the split breaks, you'll find Repo calls or Ecto.Query imports in LiveViews or controllers. Move those into the appropriate context module.

# ❌ Business logic in the web layer
defp queue_depth do
  Oban.Job |> where([j], j.state == "available") |> Repo.one()
end

# ✅ Web layer calls the context
assign(socket, :queue_depth, Jobs.queue_depth())