Laravel Modular Monolith: Bounded Contexts in Practice | Mohamed Said [ ![Mohamed Said](https://cdn.msaied.com/01KT78WE565VEMM3PSNQAAB0MH.png) Mohamed Said Laravel Backend Engineer ](https://msaied.com) [ Home ](https://msaied.com) [ Projects ](https://msaied.com/projects) [ Articles ](https://msaied.com/articles) [ Certificates ](https://msaied.com/certificates) [ Contact ](https://msaied.com#contact-section) [ ](https://github.com/EG-Mohamed) [ Home ](https://msaied.com) [ Projects ](https://msaied.com/projects) [ Articles ](https://msaied.com/articles) [ Certificates ](https://msaied.com/certificates) [ Contact ](https://msaied.com#contact-section) [ home ](https://msaied.com) [ articles ](https://msaied.com/articles) Modular Monolith in Laravel: Enforcing Bounded Contexts Without a Microservices Tax On this page 1. [ Why a Modular Monolith? ](#why-a-modular-monolith) 2. [ Module Structure ](#module-structure) 3. [ Internal Contracts: The Boundary Enforcement Mechanism ](#internal-contracts-the-boundary-enforcement-mechanism) 4. [ Enforcing the Rules with Deptrac ](#enforcing-the-rules-with-deptrac) 5. [ Cross-Module Events Instead of Direct Calls ](#cross-module-events-instead-of-direct-calls) 6. [ Shared Kernel ](#shared-kernel) 7. [ Key Takeaways ](#key-takeaways) ![Modular Monolith in Laravel: Enforcing Bounded Contexts Without a Microservices Tax](https://cdn.msaied.com/380/024b5513124d6a6f3f0588cb3f6554c3.png) #laravel #architecture #ddd #modular-monolith Modular Monolith in Laravel: Enforcing Bounded Contexts Without a Microservices Tax ===================================================================================== 6 Jul 2026 3 min read ![Mohamed Said](https://cdn.msaied.com/01KT78WE565VEMM3PSNQAAB0MJ.jpg) Mohamed Said Table of contents 1. [ 01 Why a Modular Monolith? ](#why-a-modular-monolith) 2. [ 02 Module Structure ](#module-structure) 3. [ 03 Internal Contracts: The Boundary Enforcement Mechanism ](#internal-contracts-the-boundary-enforcement-mechanism) 4. [ 04 Enforcing the Rules with Deptrac ](#enforcing-the-rules-with-deptrac) 5. [ 05 Cross-Module Events Instead of Direct Calls ](#cross-module-events-instead-of-direct-calls) 6. [ 06 Shared Kernel ](#shared-kernel) 7. [ 07 Key Takeaways ](#key-takeaways) Why a Modular Monolith? ----------------------- Microservices solve distribution problems you probably don't have yet. A modular monolith gives you the same conceptual separation — bounded contexts, explicit contracts, isolated domain logic — while keeping a single deployable, a single database transaction scope, and zero network overhead between modules. The goal is not folder organisation for its own sake. It is **preventing accidental coupling** so that the Billing team can refactor invoicing without breaking the Shipping team's code. --- Module Structure ---------------- Each bounded context lives under `app/Modules/{Context}/`. The internal layout mirrors a mini-application: ```php app/Modules/ Billing/ Actions/ Data/ # DTOs, value objects Domain/ # Eloquent models, domain services Http/ # Controllers, requests, resources Infrastructure/ # Repositories, external adapters Providers/ BillingServiceProvider.php routes.php Shipping/ ... ``` Each module registers itself via its own service provider, which is loaded from `bootstrap/providers.php` (Laravel 11+): ```php // bootstrap/providers.php return [ App\Modules\Billing\Providers\BillingServiceProvider::class, App\Modules\Shipping\Providers\ShippingServiceProvider::class, ]; ``` ```php // app/Modules/Billing/Providers/BillingServiceProvider.php class BillingServiceProvider extends ServiceProvider { public function boot(): void { $this->loadRoutesFrom(__DIR__ . '/../routes.php'); $this->loadMigrationsFrom(__DIR__ . '/../Infrastructure/Migrations'); } public function register(): void { $this->app->bind( \App\Modules\Billing\Domain\Contracts\InvoiceRepository::class, \App\Modules\Billing\Infrastructure\EloquentInvoiceRepository::class, ); } } ``` --- Internal Contracts: The Boundary Enforcement Mechanism ------------------------------------------------------ Modules must never import each other's internal classes directly. Instead, each module exposes a **public API interface** in a `Contracts` namespace: ```php // app/Modules/Billing/Contracts/BillingModuleInterface.php namespace App\Modules\Billing\Contracts; use App\Modules\Billing\Data\InvoiceData; interface BillingModuleInterface { public function issueInvoice(int $orderId, int $customerId): InvoiceData; public function getOutstandingBalance(int $customerId): Money; } ``` Shipping resolves this interface through the container — it never touches `Billing\Domain\` directly: ```php // app/Modules/Shipping/Actions/DispatchOrder.php class DispatchOrder { public function __construct( private readonly BillingModuleInterface $billing, ) {} public function handle(Order $order): void { $balance = $this->billing->getOutstandingBalance($order->customer_id); if ($balance->isNegative()) { throw new OutstandingBalanceException(); } // dispatch logic ... } } ``` --- Enforcing the Rules with Deptrac -------------------------------- Folder conventions are worthless without tooling. [Deptrac](https://github.com/qossmic/deptrac) analyses static imports and fails CI when a module reaches across a boundary: ```yaml # deptrac.yaml deptrac: paths: - app/Modules layers: - name: Billing collectors: - type: directory value: app/Modules/Billing/ - name: Shipping collectors: - type: directory value: app/Modules/Shipping/ ruleset: Shipping: - Billing # Shipping may only use Billing's public Contracts Billing: ~ ``` Run `./vendor/bin/deptrac analyse` in CI. Any direct import of `Billing\Domain\` from `Shipping\` becomes a build failure. --- Cross-Module Events Instead of Direct Calls ------------------------------------------- For truly decoupled side-effects, prefer domain events over direct method calls: ```php // Billing fires: event(new InvoicePaid($invoiceId, $customerId, $amount)); // Shipping listens in its own EventServiceProvider: Event::listen(InvoicePaid::class, ReleaseHeldShipments::class); ``` The event class lives in a shared `app/Events/` namespace (or a dedicated `app/Shared/` module) so neither context owns it. --- Shared Kernel ------------- Some primitives — `Money`, `Address`, `UserId` — are used everywhere. Place them in `app/Shared/` and treat that namespace as a read-only dependency for all modules. No module writes back to Shared. --- Key Takeaways ------------- - **One service provider per module** keeps registration isolated and explicit. - **Public contract interfaces** are the only surface other modules may depend on. - **Deptrac in CI** turns architectural rules into hard failures, not guidelines. - **Domain events** decouple side-effects without requiring a message broker. - **Shared kernel** is small and stable; resist the urge to dump utilities there. Found this useful? [ ](https://twitter.com/intent/tweet?url=https%3A%2F%2Fmsaied.com%2Farticles%2Fmodular-monolith-in-laravel-enforcing-bounded-contexts-without-a-microservices-tax-2&text=Modular+Monolith+in+Laravel%3A+Enforcing+Bounded+Contexts+Without+a+Microservices+Tax) [ ](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fmsaied.com%2Farticles%2Fmodular-monolith-in-laravel-enforcing-bounded-contexts-without-a-microservices-tax-2) Frequently Asked Questions ---------------------------- 3 questions Q01 Do I need separate databases per module? No. A modular monolith shares one database. The boundary is in code, not infrastructure. You can extract a module to a microservice later if needed, but separate databases are not a prerequisite. Q02 How do I handle shared Eloquent models that multiple modules need? Place truly shared models (e.g. User) in a Shared or Core module. Each consuming module accesses them through that shared namespace, never by reaching into another module's Domain folder. Q03 Is Deptrac the only option for enforcing boundaries? PHPArkitect is a PHP-native alternative with a fluent API. Both integrate well with GitHub Actions or any CI pipeline and serve the same purpose: turning architectural conventions into automated checks. 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