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Top 10 Senior-Level Laravel Interview Questions

Q1. What is the difference between register() and boot() in a Service Provider?
Ans. register() is only for binding things into the container, and you shouldn’t use other services there because they may not be loaded yet. boot() runs after all providers are registered, so it is the right place for event listeners, view composers and route setup.

Q2. How do you choose between chunk(), cursor() and lazy() for large datasets?
Ans. chunk() processes records in fixed-size batches. cursor() streams one record at a time with very low memory use, but it can’t eager-load relations. lazy() runs chunked queries but returns a lazy collection, which makes it a good default for large exports and data-fix scripts.

Q3. What is the difference between Gates and Policies, and when do you use each?
Ans. A Gate is a simple closure-based authorization check, suitable for small checks not tied to a model. A Policy is a class that groups all authorization rules (view, update, delete) for one Eloquent model. In larger projects, policies are easier to maintain and are used through $this->authorize() or @can.

Q4. How do Model Observers differ from Events and Listeners?
Ans. An Observer listens to a model’s lifecycle events (created, updated, deleted) in one class. Custom Events and Listeners can represent any business action, such as OrderPlaced, and one event can trigger many listeners. Keep observers light, and remember they don’t fire on bulk updates that bypass models.

Q5. What do Cache::remember() and atomic locks do in Laravel?
Ans. Cache::remember($key, $ttl, fn () => ...) returns the cached value if it exists, otherwise runs the closure and stores the result. Atomic locks (Cache::lock()) prevent cache stampedes and duplicate execution, for example stopping the same scheduled job from running twice at once.

Q6. What is the difference between Feature and Unit tests, and how do you test code that calls an external API?
Ans. A Unit test checks one small class or method in isolation. A Feature test covers a full flow, from the HTTP request to the response. For external APIs, use Http::fake() so tests don’t depend on the real network, and use the RefreshDatabase trait to keep the database clean between tests.

Q7. Why use API Resources, and how do they keep responses consistent?
Ans. API Resources transform model data into a controlled JSON format, so internal database columns are never exposed by accident. With resource collections, pagination metadata is added automatically, and it becomes easier to keep the response format stable across API versions.

Q8. How do you apply rate limiting to routes?
Ans. Use the throttle middleware and define custom limits with RateLimiter::for(), for example per user or per IP. Sensitive endpoints like login get stricter limits, and when a limit is exceeded Laravel returns 429 Too Many Requests.

Q9. Which Artisan commands do you run when deploying a Laravel app to production?
Ans. config:cache, route:cache and view:cache reduce bootstrapping time, and php artisan optimize runs these together. Remember that after config:cache, env() works only inside config files, so application code should read values with config().

Q10. How do you prevent a race condition when two users update the same stock or balance at the same time?
Ans. Wrap the update in a transaction and use lockForUpdate(), so the second request waits until the first one finishes:

DB::transaction(function () use ($id) {
    $product = Product::lockForUpdate()->find($id);
    $product->decrement('stock');
});