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[Home](https://www.msaied.com/public) 2. / 3. [Articles](https://www.msaied.com/public/articles) 4. / 5. Modular Monolith in Laravel: Enforcing Bounded Contexts Without a Microservices Tax Modular Monolith in Laravel: Enforcing Bounded Contexts Without a Microservices Tax ==================================================================================== Learn how to slice a Laravel application into cohesive bounded contexts using modules, internal contracts, and cross-module event dispatch — without splitting into microservices or fighting the framework. ![](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp) [Mohamed Said](https://www.msaied.com/public#person) Published 28 Jun 2026 · Updated 28 Jun 2026 · 3 min read ShareCopy linkCopied ![Modular Monolith in Laravel: Enforcing Bounded Contexts Without a Microservices Tax](https://cdn.msaied.com/316/45b214e7656a6fe4e1c42a427f394287.png) On this page +1. [Why a Modular Monolith?](#why-a-modular-monolith) 2. [Directory Layout](#directory-layout) 3. [Internal Contracts: The Only Crossing Point](#internal-contracts-the-only-crossing-point) 4. [Cross-Module Communication via Domain Events](#cross-module-communication-via-domain-events) 5. [Enforcing Boundaries with Deptrac](#enforcing-boundaries-with-deptrac) 6. [Shared Kernel: What Belongs There](#shared-kernel-what-belongs-there) 7. [Key Takeaways](#key-takeaways) Why a Modular Monolith? ----------------------- Microservices promise isolation but deliver operational complexity. A well-structured modular monolith gives you the same conceptual boundaries — bounded contexts, explicit contracts, independent domain logic — while keeping deployment, transactions, and debugging simple. The goal is not to split the codebase into packages. It is to enforce rules about *who may call whom* and *how* at the PHP level, so the boundaries are real rather than aspirational. --- Directory Layout ---------------- Each bounded context lives under `src/Modules/`. The framework's `app/` directory becomes a thin bootstrap layer. ```javascript src/ Modules/ Billing/ Actions/ Data/ Events/ Http/ Models/ Contracts/ BillingServiceInterface.php BillingServiceProvider.php Catalog/ ... Identity/ ... app/ Providers/ AppServiceProvider.php ← registers module providers only ``` Each module registers itself via its own `ServiceProvider`. `AppServiceProvider` does nothing but call `$this->app->register(BillingServiceProvider::class)` for each module. --- Internal Contracts: The Only Crossing Point ------------------------------------------- Modules must never import each other's concrete classes. They communicate through interfaces declared in their own `Contracts/` namespace. ```php // src/Modules/Billing/Contracts/BillingServiceInterface.php namespace Modules\Billing\Contracts; interface BillingServiceInterface { public function charge(string $customerId, int $amountCents): ChargeResult; } ``` The `Catalog` module depends on this interface, not on `Modules\Billing\Services\StripeService`. ```php // src/Modules/Catalog/Actions/PublishProduct.php namespace Modules\Catalog\Actions; use Modules\Billing\Contracts\BillingServiceInterface; final class PublishProduct { public function __construct( private readonly BillingServiceInterface $billing ) {} public function handle(Product $product): void { $result = $this->billing->charge($product->owner_id, $product->listing_fee_cents); // ... } } ``` Binding the concrete implementation happens inside `BillingServiceProvider`, invisible to the caller. ```php // src/Modules/Billing/BillingServiceProvider.php $this->app->bind( \Modules\Billing\Contracts\BillingServiceInterface::class, \Modules\Billing\Services\StripeService::class, ); ``` --- Cross-Module Communication via Domain Events -------------------------------------------- When a module needs to *notify* rather than *query*, use Laravel's event dispatcher with typed event classes. Each module listens only to events it cares about. ```php // src/Modules/Identity/Events/UserRegistered.php namespace Modules\Identity\Events; final class UserRegistered { public function __construct( public readonly string $userId, public readonly string $email, ) {} } ``` ```php // src/Modules/Billing/Listeners/ProvisionFreeTier.php namespace Modules\Billing\Listeners; use Modules\Identity\Events\UserRegistered; final class ProvisionFreeTier { public function handle(UserRegistered $event): void { // create a free subscription for $event->userId } } ``` The `Identity` module fires the event and has zero knowledge of `Billing`. The listener is registered in `BillingServiceProvider`: ```php $this->listen(UserRegistered::class, ProvisionFreeTier::class); ``` --- Enforcing Boundaries with Deptrac --------------------------------- Conventions break under deadline pressure. Automate enforcement with [Deptrac](https://qossmic.github.io/deptrac/): ```yaml # deptrac.yaml layers: - name: Billing collectors: - type: className regex: ^Modules\\Billing\\ - name: Catalog collectors: - type: className regex: ^Modules\\Catalog\\ ruleset: Catalog: - Billing # Catalog may only use Billing's Contracts, enforced by regex Billing: [] ``` Run `deptrac analyse` in CI. Any direct import of a concrete class across module boundaries fails the build. --- Shared Kernel: What Belongs There --------------------------------- Not everything is module-specific. A `Shared/` kernel holds: - Base value objects (`Money`, `Email`, `Uuid`) - Common exceptions (`DomainException`, `ValidationException`) - Infrastructure interfaces (`ClockInterface`, `UuidGeneratorInterface`) Modules may depend on `Shared/`. `Shared/` must never depend on any module. --- Key Takeaways ------------- - **Modules own their service providers** — binding, listening, and scheduling stay inside the module. - **Contracts are the only public API** — no concrete class crosses a module boundary. - **Events decouple producers from consumers** — the firing module never imports the listener. - **Deptrac in CI makes boundaries real** — conventions without tooling are just comments. - **Shared kernel stays thin** — value objects and interfaces only, no business logic. - **Transactions still work** — because it is one process and one database connection, `DB::transaction()` spans modules freely. - [laravel](https://www.msaied.com/public/articles?search=laravel) - [architecture](https://www.msaied.com/public/articles?search=architecture) - [ddd](https://www.msaied.com/public/articles?search=ddd) - [modular-monolith](https://www.msaied.com/public/articles?search=modular-monolith) Frequently asked questions --------------------------- How is this different from just organising files into folders?The difference is enforcement. Folder organisation is cosmetic. Bounded contexts backed by interface-only contracts and Deptrac CI rules make illegal dependencies a build failure, not a code-review suggestion. Can modules share an Eloquent model, for example a User?Avoid it. Instead, each module defines a read-only projection or a lightweight DTO for the data it needs. The Identity module owns the User model; other modules query through a contract method or listen to events. Does this approach work with Filament admin panels?Yes. Each module can register its own Filament resources inside its ServiceProvider using Filament::serving(). The panel itself lives in a dedicated Module\\Admin context that imports only contracts from other modules. ![Mohamed Said](https://cdn.msaied.com/01M22N44A70A5MC2S599JP0MPH.webp)About the author ---------------- [Mohamed Said](https://www.msaied.com/public#person)Senior Backend Engineer specializing in Laravel, scalable SaaS platforms, APIs, and cloud infrastructure. I build secure, high-performance web applications that help businesses grow. [About](https://www.msaied.com/public#about) [GitHub ↗](https://github.com/EG-Mohamed) [LinkedIn ↗](https://www.linkedin.com/in/msaiedm/) [WhatsApp ↗](https://wa.me/201094619204) [Email Address ↗](mailto:hello@msaied.com) [My CV ↗](https://drive.google.com/file/u/0/d/1MF20IPRJyzfy32mhEutjL5EpSls0w2Q8/view) [Previous articleEvent Sourcing and CQRS in Laravel: Aggregates, Projectors, and Eventual Consistency](https://www.msaied.com/public/articles/event-sourcing-and-cqrs-in-laravel-aggregates-projectors-and-eventual-consistency) [Next articleDDD in Laravel: Actions, DTOs, and Value Objects Without the Bloat](https://www.msaied.com/public/articles/ddd-in-laravel-actions-dtos-and-value-objects-without-the-bloat) On this page ------------- 1. [Why a Modular Monolith?](#why-a-modular-monolith) 2. [Directory Layout](#directory-layout) 3. [Internal Contracts: The Only Crossing Point](#internal-contracts-the-only-crossing-point) 4. [Cross-Module Communication via Domain Events](#cross-module-communication-via-domain-events) 5. [Enforcing Boundaries with Deptrac](#enforcing-boundaries-with-deptrac) 6. [Shared Kernel: What Belongs There](#shared-kernel-what-belongs-there) 7. [Key Takeaways](#key-takeaways) ### Have a technical challenge? Tell me what you’re building. I reply within two working days. 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