Domain Driven Design (DDD) Pattern for Our Agency

We organize code by domain boundaries — each domain represents a core business concept and contains all related logic, UI, data, and tests in one place. This makes scaling and maintenance straightforward.

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Domain Folder Structure Explained

index.ts — The Barrel File

Acts as the public API for the domain. Controls what other parts of the app can import from this domain, enforcing clear boundaries.

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composables/

Houses Vue composables related to the domain. These are reusable reactive hooks used inside Vue components (setup context).

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services/

This is where the business logic lives — all domain-specific rules, workflows, and processes.
Also contains model.ts which defines the domain’s data shapes and validation schemas.

Example:

// services/model.ts
export interface User {
    id: string
    email: string
    active: boolean
    // etc.
}

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data/

The data access layer — acts as an API between the database (e.g. Firebase) and the domain.
Provides standard CRUD-like methods abstracted away from the rest of the domain, so changes to DB tech won’t ripple through your business logic.

const UserData = {
    set: (userId: string, data: Partial<User>) => {
        ;/_ update DB _/
    },
    get: (userId: string) => {
        ;/_ fetch from DB _/
    },
    has: (userId: string) => {
        ;/_ check existence _/
    },
    delete: (userId: string) => {
        ;/_ remove from DB _/
    },
}

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types/

Contains domain-specific TypeScript types, interfaces, and DTOs (data transfer objects). Keeps your domain strongly typed and consistent.

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tests/

Unit and integration tests specific to the domain. Keeps tests close to the domain code for easy maintenance.

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Summary

• Domains are self-contained feature modules with all related code.
• index.ts controls the domain’s external API (export only what’s needed).
• Services contain business rules without leaking infrastructure code.
• Data abstracts database operations for flexibility and isolation.
• Keeps code modular, testable, and scalable — perfect for SaaS agencies. s