Vertical Slice Architecture

Overview

Vertical slice architecture, popularized by Jimmy Bogard, flips the usual layout. Instead of grouping by technical role, it groups by feature. To change how an order is placed, you open one folder.

How it works

Each request is handled by a handler within its slice, often via a mediator.

features/
  place-order/    PlaceOrder.cs  (request, validator, handler, SQL)
  cancel-order/   CancelOrder.cs
  get-invoice/    GetInvoice.cs
  shared/         only proven reusable code

export async function placeOrder(cmd: PlaceOrder, db: Db) {
  validate(cmd)
  const stock = await db.query("select qty from stock where sku = $1", [cmd.sku])
  if (stock < cmd.qty) throw new OutOfStock()
  await db.exec("insert into orders ...")
}

A simple read slice can query the database directly and return a DTO. A complex command slice can load an aggregate and invoke domain methods. Rules shared by several slices live in the domain model, not in a generic service layer.

Pitfalls

• Slices invoking other slices, which creates tangled implicit dependencies.
• Abstracting too early; wait for the third repetition before extracting.
• Skipping a domain model where invariants clearly span slices.
• Having no conventions, so each slice looks different.
• Using it as an excuse for no architecture tests.

Key takeaways

• Organize by what changes together.
• Let each slice choose its own design depth.
• Share only what has proven shared.
• Keep invariants in a common domain model when they cross slices.