API Design for Startups: Backends That Don't Break Frontends

Whether you're building a startup app or an internal API, you'll likely need a backend that frontends and integrations can rely on. The API you build today will either make your life easier or become a constant source of frustration. Here's how to build it right with Laravel—practical advice I use with clients across Bath, Bristol, and Wiltshire. See also database design for startups and scaling Laravel backends.

Start with REST, Keep It Simple

REST is still the right choice for most startup APIs. It's well-understood, has great tooling, and Laravel makes it easy to build. Don't overthink it with GraphQL or gRPC unless you have a specific need.

Laravel's API resources make it trivial to transform your models into consistent JSON responses:

// app/Http/Resources/UserResource.php
class UserResource extends JsonResource
{
    public function toArray($request)
    {
        return [
            'id' => $this->id,
            'name' => $this->name,
            'email' => $this->email,
            'created_at' => $this->created_at->toIso8601String(),
        ];
    }
}

Version Your API from Day One

You will change your API. Version it from the start so you don't break existing clients when you need to make changes.

In Laravel, this is as simple as:

Route::prefix('v1')->group(function () {
    Route::apiResource('users', UserController::class);
});

// Later, when you need changes:
Route::prefix('v2')->group(function () {
    Route::apiResource('users', UserController::class);
});

Keep v1 working, add v2 with improvements. Your mobile app can migrate when ready.

Consistent Response Formats

Nothing frustrates frontend developers more than inconsistent API responses. Use a standard format:

// Success response
{
    "data": { ... },
    "meta": { ... }  // optional
}

// Error response
{
    "error": {
        "message": "Validation failed",
        "errors": { ... }
    }
}

Laravel's API resources handle this well, and you can create a base response class to ensure consistency.

Pagination Done Right

If your API returns lists, paginate them. Always. Even if you only have 10 items today, you'll have 10,000 tomorrow.

Laravel's pagination is perfect for this:

// In your controller
return UserResource::collection(
    User::paginate(20)
);

// Response includes:
{
    "data": [...],
    "links": {
        "first": "...",
        "last": "...",
        "prev": null,
        "next": "..."
    },
    "meta": {
        "current_page": 1,
        "per_page": 20,
        "total": 100
    }
}

Filtering and Sorting

Your frontend will need to filter and sort. Build this into your API from the start:

// GET /api/v1/users?status=active&sort=name&order=asc
public function index(Request $request)
{
    $query = User::query();

    if ($request->has('status')) {
        $query->where('status', $request->status);
    }

    if ($request->has('sort')) {
        $query->orderBy(
            $request->sort,
            $request->get('order', 'asc')
        );
    }

    return UserResource::collection($query->paginate(20));
}

Error Handling

Handle errors gracefully. Use HTTP status codes correctly:

• 200: Success
• 201: Created
• 400: Bad request (validation errors)
• 401: Unauthorized
• 404: Not found
• 422: Unprocessable entity (validation)
• 500: Server error

Laravel's exception handling makes this easy. Customize your exception handler to return consistent error formats.

Authentication: Use Laravel Sanctum

For most startup APIs, Laravel Sanctum is perfect. It's simple, secure, and works great for:

• SPA (Single Page Applications)
• Mobile applications
• Simple token-based authentication

It's built into Laravel and much simpler than Passport for most use cases.

Documentation Matters

Document your API. I'm a big fan of OpenAPI (Swagger) documentation. It's a standard that's easy to generate from your code and easy to understand. Laravel has several packages available that create API documentation automatically from the code, ensuring it's always up to date and available to your team and clients.

As a minimum, you should document:

• Available endpoints
• Request/response formats
• Authentication requirements
• Error responses

Good documentation saves hours of back-and-forth with frontend developers.

Testing Your API

Write tests for your API endpoints. Laravel's HTTP tests make this easy:

public function test_can_create_user()
{
    $response = $this->postJson('/api/v1/users', [
        'name' => 'John Doe',
        'email' => 'john@example.com',
    ]);

    $response->assertStatus(201)
             ->assertJsonStructure([
                 'data' => ['id', 'name', 'email']
             ]);
}

The Bottom Line

A well-designed API is a joy to work with. It's consistent, predictable, and makes frontend development faster. A poorly designed API causes constant friction and slows down your entire team.

Start simple, be consistent, version early, and document as you go. Your future self (and your frontend developers) will thank you. Related reading: database design for Laravel applications and scaling your Laravel backend. For when to hire a Laravel developer locally, see Laravel developer in Bath & Bristol.

If you're building an API in Bath, Bristol, or Wiltshire and need help getting it right, let's talk. As a freelance developer I help startups and product teams across the UK build maintainable, scalable APIs with Laravel.