🎯 Cracking the Interview: Networking Essentials for Android Engineers

Blog InfosAuthorLeo NPublished29. January 2025Topicsandroid, Android App Development, AndroidDev, Networking, Technical InterviewAuthorLeo NPublished29. January 2025Topicsandroid, Android App Development, AndroidDev, Networking, Technical InterviewFacebookTwitter

The network interview round is designed to dive deep into your understanding of networking fundamentals, especially as they relate to Android development. This round is conducted by the Hiring Manager and focuses on assessing your ability to handle critical aspects of networking, such as security, performance optimization, and offline capabilities.

In this article, we’ll explore the most common networking questions, practical examples, and strategies to excel in this round. From understanding HTTP/HTTPS protocols, DNS resolution, CDN mechanisms and WebSocket to debugging tools and implementing secure network communication, this guide equips you with the knowledge to shine in your interview. Let’s get started!

References

Conclusion

Http2 vs Http3?

What is QUIC?

WebSocket Latency Optimization

Questions

Questions

01. Explain the HTTP and HTTPS protocols.

• HTTP (HyperText Transfer Protocol): A protocol for transferring data over the web. It is stateless and not secure, meaning the data is sent in plain text.
• HTTPS (HTTP Secure): An extension of HTTP that uses SSL/TLS to encrypt the data, ensuring confidentiality, integrity, and authenticity.

 02. SSL/TLS Handshake Steps:

1. Client sends a “Hello” message with supported cryptographic algorithms.
2. Server responds with its SSL certificate and chosen algorithm.
3. Client verifies the certificate and generates a session key, encrypting it with the server’s public key.
4. Server decrypts the session key, and encrypted communication begins.

03. What are the different HTTP methods, and when would you use them?

• GET: Retrieve data. Example: Fetching a user’s profile.
• POST: Submit data to the server. Example: Creating a new user.
• PUT: Update a resource entirely. Example: Updating user details.
• PATCH: Partially update a resource. Example: Changing only the email of a user.
• DELETE: Remove a resource. Example: Deleting a post.

04. How would you handle offline mode in an Android app?

Techniques:

• Use Room Database or SharedPreferences to store data locally.
• Check connectivity using ConnectivityManager.
• Use WorkManager to retry failed requests when the device is back online.

Example: Save network responses in Room and display them when offline.

05. How do you ensure data security during network communication in an Android app?

• Use SSL Pinning to bind the app to a specific SSL certificate.
• Implement OAuth 2.0 for authentication.
• Avoid hardcoding sensitive information. Use Android KeyStore for secure storage.

06. How does DNS work?

• DNS translates human-readable domain names (e.g., google.com) to IP addresses.

Steps:

• User enters a domain name.
• The browser checks its local cache.
• If not found, a recursive DNS resolver queries authoritative DNS servers.
• The IP address is returned and used to connect to the server.

07. What is a CDN, and how does it improve performance?

A CDN (Content Delivery Network) is a distributed network of servers designed to deliver content to users more efficiently by minimizing latency and optimizing the transfer of data. CDNs are widely used to improve the performance, speed, and reliability of websites and applications by caching content closer to the user’s geographical location.

Content Distribution:

• Content (e.g., HTML, CSS, JavaScript, images, videos, APIs) is stored on a network of servers called edge servers located in multiple geographic locations.
• When a user requests content, the request is routed to the nearest edge server instead of the origin server, reducing latency.

Caching:

• Frequently requested content is cached on edge servers, reducing the need to fetch data from the origin server repeatedly.
• Dynamic content can also be optimized by CDNs using advanced techniques like real-time caching and compression.

Load Balancing: CDNs distribute traffic across multiple servers to prevent overload and ensure reliable service, especially during traffic spikes.

Failover and Redundancy: If one server fails, CDNs automatically reroute traffic to another server, ensuring high availability.

Geolocation and DNS Resolution:

• CDNs use the user’s IP address and DNS to determine the closest edge server.
• DNS resolution maps the user request to the nearest server, optimizing delivery time.

Common CDN Providers

• Akamai: One of the largest and oldest CDN providers.
• Cloudflare: Offers CDN services with additional security features.
• Amazon CloudFront: Integrated with AWS services.
• Google Cloud CDN: Optimized for Google Cloud Platform.
• Fastly: Focused on real-time and dynamic content delivery.

Key Benefits of CDNs

Improved Performance:

• Reduced latency as data is delivered from servers closer to users.
• Optimized routing and reduced packet loss.

Scalability: Handles large traffic volumes and spikes, such as during sales events or viral content.

Reliability: Redundant servers ensure high availability even in case of server failures.

Security:

• Protection against DDoS attacks through traffic filtering and rate limiting.
• Secure delivery using TLS/SSL encryption.

Cost Savings: Reduced bandwidth costs for origin servers as content is served from edge servers.

<!-- Without CDN -->
<script src="/js/jquery.min.js"></script>

<!-- With CDN -->
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>

08. What are WebSockets, and how do they differ from REST APIs?

WebSocket: WebSocket is a full-duplex communication protocol over a single TCP connection, enabling real-time, bi-directional communication between a client and a server.

REST API: Stateless, one-way communication.

Comparison with HTTP:

• Connection Type:
  HTTP is stateless and uses a request-response model, while WebSocket maintains a persistent connection for continuous communication.
• Efficiency:
  WebSocket avoids the overhead of repeatedly opening and closing connections, making it suitable for real-time updates.
• Use Cases:
  WebSocket is ideal for applications requiring live updates (e.g., chat, real-time stock prices), whereas HTTP is suitable for standard, non-real-time web requests.

09. How would you implement retry logic in network calls?

• Use Retrofit’s Interceptor or CallAdapter for retries.
• Example: Exponential backoff to wait longer between retries for server overload scenarios.

10. What is the difference between synchronous and asynchronous network requests?

• Synchronous: Blocks the thread until the response is received.
• Asynchronous: Uses callbacks, coroutines, or RxJava to process requests in the background without blocking the UI thread.

11. How do you debug network issues in an Android app?

• Use Charles Proxy or Postman or HttpToolKit to inspect requests and responses.
• Analyze logs in Logcat.
• Check for issues like incorrect endpoints, timeouts, or SSL errors.

12. Explain the difference between TCP and UDP.

• TCP (Transmission Control Protocol): Reliable, ensures data arrives in order. Used for apps like HTTP, email.
• UDP (User Datagram Protocol): Faster, does not guarantee delivery. Used for real-time apps like VoIP, video streaming.

13. How would you optimize a slow API response in your app?

• Cache responses using OkHttp or Room.
• Use compression like Gzip for payloads.
• Reduce payload size by only sending necessary fields.

14. How does a proxy server work, and how is it different from a VPN?

• Proxy Server: Forwards requests between clients and servers, often for filtering or caching.
• VPN: Encrypts data and masks IP addresses for privacy and security.

15. What are some common security vulnerabilities in networking?

• MITM (Man-in-the-Middle): Prevented by using HTTPS and SSL pinning.
• CSRF (Cross-Site Request Forgery): Use tokens for validation.
• CORS Issues: Configure proper CORS policies on the server.

16. How do you monitor and log network performance in Android?

• Use Firebase Performance Monitoring or custom analytics tools.
• Log metrics like request latency and error rates in Logcat.

17. What are the differences between http 1.1 and http 2?

HTTP/2 is a major revision of the HTTP network protocol used by the World Wide Web. One key difference between HTTP 1.1 and HTTP/2 is the way in which data is sent between the client and server.

1⃣ Multiplexing:

HTTP/1.1

• Relies on multiple connections to load various resources, leading to head-of-line blocking issues and slower page load times.
• Only one request per connection at a time.
• To handle multiple requests, browsers open multiple TCP connections, leading to connection overhead.

HTTP/2

• Allows multiple requests and responses to be multiplexed over a single connection, improving efficiency and reducing latency.
• Reduces connection overhead and improves performance.

2⃣ Binary Protocol:

HTTP/1.1

• Text-based protocol
• Requests and responses are transmitted as plain text.

HTTP/2

• Binary protocol.
• Encodes data in a compact and efficient binary format, reducing parsing overhead and errors.

3⃣ Server Push

HTTP/1.1

• The server can only respond to client requests.
• No proactive mechanism to send resources.

HTTP/2

• Supports server push, where the server can preemptively send resources (like CSS or JavaScript files) that it anticipates client need.
• Reduces page load times.

4⃣ Security

HTTP/1.1

• Can work over plain text (HTTP) or encrypted connections (HTTPS).

HTTP/2

• Encrypted by default. Most implementations require TLS 1.2 or higher

HTTP/2 brings significant improvements in efficiency, speed, and resource usage compared to HTTP/1.1. It is particularly beneficial for modern web applications with high resource demands, making it the preferred protocol for web development today.

18. How does WebSocket work (Handshake, maintaining connection, closing connection)?

• Handshake:
  A WebSocket connection starts with an HTTP request (with an Upgrade header) to upgrade to the WebSocket protocol. If successful, the server responds with a 101 Switching Protocols status.
• Maintaining Connection:
  Once the connection is established, the server and client can freely send messages in both directions without re-establishing the connection.
• Closing Connection:
  Either party can send a “Close Frame,” followed by a proper closure of the underlying TCP connection.

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