Interview questions - full stack Developer(.net/auzre)

Below are best-practice answers to the common interview questions I listed earlier. These answers are designed to be concise, clear, and demonstrate your expertise.

---

.NET Questions

1. What is the difference between IEnumerable and IQueryable?

• IEnumerable:

  • Works with in-memory collections (e.g., List, Array).

  • Executes queries on the client side (LINQ-to-Objects).

  • Suitable for small datasets.

• IQueryable:

  • Works with remote data sources (e.g., databases).

  • Executes queries on the server side (LINQ-to-Entities).

  • Suitable for large datasets and optimized for performance.

• Example:

  csharp

  Copy

  IEnumerable<Customer> customers = db.Customers.Where(c => c.Age > 30).ToList(); // Executes in memory
  IQueryable<Customer> customers = db.Customers.Where(c => c.Age > 30); // Executes on the database server

---

2. How does dependency injection work in ASP.NET Core?

• Dependency Injection (DI) is a design pattern used to achieve Inversion of Control (IoC) between classes and their dependencies.

• How it works:

  • Services are registered in the Startup.cs or Program.cs file using services.AddSingleton, services.AddScoped, or services.AddTransient.

  • The framework injects these services into controllers, views, or other services via constructor injection.

• Example:

  csharp

  Copy

  public void ConfigureServices(IServiceCollection services)
  {
      services.AddScoped<IMyService, MyService>(); // Register service
  }
  
  public class MyController : Controller
  {
      private readonly IMyService _myService;
      public MyController(IMyService myService) // Inject service
      {
          _myService = myService;
      }
  }

---

3. Explain the lifecycle of a .NET application.

• Compilation:

  • Source code is compiled into Intermediate Language (IL) by the C# compiler.

• Execution:

  • The Common Language Runtime (CLR) loads the IL code and compiles it into machine code using Just-In-Time (JIT) compilation.

• Memory Management:

  • The Garbage Collector (GC) automatically manages memory allocation and deallocation.

• Application Domains:

  • .NET applications run in isolated environments called application domains.

---

4. What is the difference between Task and Thread in C#?

• Thread:

  • Represents an actual OS-level thread.

  • Resource-intensive and harder to manage.

• Task:

  • Represents an asynchronous operation.

  • Uses the ThreadPool for efficient resource management.

  • Supports async/await for easier asynchronous programming.

• Example:

  csharp

  Copy

  // Thread
  Thread thread = new Thread(() => DoWork());
  thread.Start();
  
  // Task
  Task.Run(() => DoWork());

---

5. How do you handle exceptions globally in ASP.NET Core?

• Use middleware to handle exceptions globally.

• Example:

  csharp

  Copy

  public void Configure(IApplicationBuilder app, IHostingEnvironment env)
  {
      if (env.IsDevelopment())
      {
          app.UseDeveloperExceptionPage();
      }
      else
      {
          app.UseExceptionHandler("/Home/Error"); // Global exception handler
      }
  }

---

Azure Questions

1. What is the difference between Azure App Service and Azure Functions?

• Azure App Service:

  • Used for hosting web applications, APIs, and mobile backends.

  • Supports multiple languages and frameworks.

  • Ideal for long-running applications.

• Azure Functions:

  • Serverless compute service for event-driven tasks.

  • Executes code in response to triggers (e.g., HTTP, timers, queues).

  • Ideal for short-lived, stateless functions.

---

2. How do you secure an Azure SQL Database?

• Authentication:

  • Use Azure Active Directory (AAD) or SQL authentication.

• Authorization:

  • Implement Role-Based Access Control (RBAC).

• Encryption:

  • Enable Transparent Data Encryption (TDE) for data at rest.

  • Use SSL/TLS for data in transit.

• Firewall Rules:

  • Restrict access to specific IP addresses or virtual networks.

---

3. Explain the difference between Azure Blob Storage and Azure Table Storage.

• Azure Blob Storage:

  • Used for storing unstructured data like images, videos, and documents.

  • Supports tiered storage (Hot, Cool, Archive).

• Azure Table Storage:

  • NoSQL key-value store for structured data.

  • Ideal for storing metadata or semi-structured data.

---

4. How do you implement CI/CD using Azure DevOps?

• Steps:

  1. Create a repository in Azure DevOps.

  2. Define a build pipeline (e.g., using YAML) to compile and test the code.

  3. Define a release pipeline to deploy the application to Azure.

  4. Use triggers to automate the process (e.g., on code push).

• Example:

  yaml

  Copy

  trigger:
    branches:
      include:
        - main
  
  pool:
    vmImage: 'windows-latest'
  
  steps:
  - task: UseDotNet@2
    inputs:
      packageType: 'sdk'
      version: '6.x'
  - script: dotnet build --configuration Release
  - script: dotnet test

---

5. What is the purpose of Azure Active Directory (AAD)?

• AAD is a cloud-based identity and access management service.

• Key Features:

  • Single Sign-On (SSO) for applications.

  • Multi-Factor Authentication (MFA) for enhanced security.

  • Integration with on-premises Active Directory.

---

Full Stack Questions

1. How do you optimize the performance of a web application?

• Frontend:

  • Minify and bundle CSS/JS files.

  • Use lazy loading for images and components.

• Backend:

  • Optimize database queries and use caching (e.g., Redis).

  • Use asynchronous programming to avoid blocking threads.

• Infrastructure:

  • Scale horizontally using load balancers.

  • Use Content Delivery Networks (CDNs) for static assets.

---

2. What are the differences between REST and GraphQL?

• REST:

  • Uses fixed endpoints for resources.

  • Over-fetching or under-fetching of data can occur.

• GraphQL:

  • Uses a single endpoint for all queries.

  • Clients can request only the data they need.

---

3. How do you handle state management in a frontend application?

• Local State:

  • Use component state (e.g., React useState).

• Global State:

  • Use state management libraries like Redux or Context API.

• Server State:

  • Use libraries like React Query or SWR for caching and synchronization.

---

4. Explain the concept of microservices and when to use them.

• Microservices:

  • Architectural style where applications are built as a collection of small, independent services.

• When to Use:

  • For large, complex applications requiring scalability and flexibility.

  • When different teams work on different parts of the application.

---

5. How do you ensure security in a full stack application?

• Authentication:

  • Use OAuth, JWT, or AAD for secure authentication.

• Authorization:

  • Implement role-based access control (RBAC).

• Data Protection:

  • Encrypt sensitive data at rest and in transit.

• Input Validation:

  • Sanitize user inputs to prevent SQL injection and XSS attacks.