Subify

Modular SaaS Subscription & Billing API

Subify is an enterprise-grade subscription management engine designed for high-scale SaaS applications. Built on a modular monolith architecture, it leverages advanced design patterns to decouple billing logic, making it easy to swap payment providers, define complex billing cycles, and maintain strict data integrity.

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🛠 Tech Stack

Component	Technology	Description
Framework	Laravel 12	The latest bleeding-edge framework version.
Language	PHP 8.4	Strong typing and performance features.
Database	PostgreSQL	Utilizing JSONB for flexible plan feature storage.
Cache	Redis	High-speed caching and queue management.
Architecture	Domain-Driven Design	Modular structure located in app/Domains.

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✨ Key Features

Subify is engineered for maintainability and scalability.

• 🚀 Pipeline Pattern Complex subscription flow logic is decoupled into reusable pipes (Validate -> Charge -> Activate). This allows you to inject or remove steps (like fraud checks or provisioning) without touching the core controller.

• 💳 Strategy Pattern Payment Gateway abstraction allowing hot-swap between Stripe, PayPal, or custom providers. The system depends on the interface, not the implementation.

• 🛡️ Strict DTOs I avoid "array hell" by using spatie/laravel-data. Every input is validated and cast to a strict Data Transfer Object before it reaches domain logic.

• 💾 JSONB Snapshots Plans change, but historical subscriptions shouldn't. I store an immutable snapshot of plan features at the time of subscription using PostgreSQL JSONB, ensuring grandfathered pricing works out of the box.

• 🏗️ Modular Monolith The codebase follows strict Domain-Driven Design (DDD) principles. All subscription logic lives in app/Domains/Subscription, isolating it from the rest of the application.

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📖 Architecture

The subscription creation process follows a strict linear pipeline, ensuring that a user is only subscribed if all previous steps (validation, payment) succeed.

graph LR
    A["API Request (DTO)"] --> B(Pipeline Start)
    B --> C{"Check Availability Pipe"}
    C -->|Success| D["Payment Pipe (Strategy)"]
    D -->|Charged| E["Save Subscription Pipe"]
    E --> F[Return Model]
    C -->|Fail| G[Exception]
    D -->|Fail| G

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🔌 API Reference

Create a Subscription

Initiate a new subscription for a user.

Endpoint: POST /api/subscriptions

Request Body

{
  "user_id": 105,
  "plan": "premium_yearly",
  "payment_method_id": "pm_card_visa",
  "options": {
    "coupon": "SUMMER_SALE_2026",
    "metadata": {
      "source": "landing_page_v2"
    }
  }
}

Response (201 Created)

{
  "data": {
    "id": "sub_1Qj2M5L...",
    "status": "active",
    "plan_snapshot": {
        "name": "Premium Yearly",
        "price": 9900,
        "currency": "USD"
    },
    "current_period_start": "2026-01-27T14:30:00Z",
    "current_period_end": "2027-01-27T14:30:00Z"
  }
}

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⚙️ Configuration

Copy the example environment file and configure your keys.

Variable	Description	Default
PAYMENT_GATEWAY	Default payment driver (stripe, fake).	stripe
STRIPE_KEY	Your Stripe Secret Key.	-
STRIPE_WEBHOOK_SECRET	Secret for verifying webhook signatures.	-
DB_CONNECTION	Database connection.	pgsql

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🚀 Installation & Testing

Quick Start

Get up and running with Docker and Laravel Sail.

# 1. Clone the repository
git clone https://github.com/web-inwall/subify.git
cd subify

# 2. Install Dependencies
composer install

# 3. Setup Environment
cp .env.example .env

# 4. Start Containers
./vendor/bin/sail up -d

# 5. Run Migrations
./vendor/bin/sail artisan migrate

Testing Pipelines

I take testing seriously. Run the test suite to see how I mock the Payment Strategy in unit and feature tests.

php artisan test

Note: The FakePaymentAdapter is used by default in the testing environment, so no actual API calls are made during CI/CD.