src/MyApp.Api/
  Features/
    Orders/CreateOrder.cs    # Request + Handler + Response + Endpoint
    Orders/GetOrder.cs
  Common/
    Behaviors/ValidationBehavior.cs
    Persistence/AppDbContext.cs

src/
  MyApp.Domain/              # Entities, interfaces, domain logic
  MyApp.Application/         # Use cases, DTOs, validation
  MyApp.Infrastructure/      # EF Core, external services
  MyApp.Api/                 # Endpoints, middleware

src/
  MyApp.Domain/              # Aggregates, value objects, domain events, domain services
  MyApp.Application/         # Use cases orchestrating aggregates
  MyApp.Infrastructure/      # Persistence, external service adapters
  MyApp.Api/                 # Thin endpoints

src/
  MyApp.Host/                # Wires modules together
  Modules/
    Orders/                  # Own features, own DbContext, own architecture
    Catalog/                 # Can use VSA, CA, or DDD internally
  MyApp.Shared/              # Integration event contracts only

// BAD — 4 projects, 6+ files per feature for simple CRUD
src/MyApp.Domain/Entities/Product.cs
src/MyApp.Application/Products/CreateProduct/CreateProductCommand.cs
src/MyApp.Application/Products/CreateProduct/CreateProductHandler.cs
src/MyApp.Application/Products/CreateProduct/CreateProductValidator.cs
src/MyApp.Infrastructure/Persistence/ProductRepository.cs
src/MyApp.Api/Endpoints/ProductEndpoints.cs

// GOOD — VSA: 1 file for a simple CRUD feature
src/MyApp.Api/Features/Products/CreateProduct.cs

// BAD — value objects and aggregates for a settings table
public class UserSettings : AggregateRoot  // overkill
{
    public ThemeName Theme { get; private set; }  // value object for "dark"/"light"?
    public void ChangeTheme(ThemeName theme) { /* domain event? really? */ }
}

// GOOD — simple entity for simple data
public class UserSettings
{
    public Guid UserId { get; init; }
    public string Theme { get; set; } = "light";
}

// BAD — splitting into 5 microservices on day one with 2 developers
OrderService (own repo, own DB, own CI/CD)
CatalogService (own repo, own DB, own CI/CD)
IdentityService (own repo, own DB, own CI/CD)
NotificationService (own repo, own DB, own CI/CD)
GatewayService (own repo, own CI/CD)

// GOOD — start as a modular monolith, extract when you have evidence
src/
  Modules/Orders/
  Modules/Catalog/
  Modules/Identity/
  Modules/Notifications/

// BAD — "I always use Clean Architecture"
User: "Set up a new project for a todo app"
Agent: *immediately scaffolds 4-project CA solution*

// GOOD — ask first, then recommend
User: "Set up a new project for a todo app"
Agent: "Let me ask a few questions about your project to recommend the best architecture..."
Agent: *runs questionnaire, recommends VSA for low-complexity app*