Designing a Networking Library in Android
Key components you should discuss in a system design interview
As we all know, most companies today have a system design round in their Android interview process.
Today, I’ll list all the components you should consider discussing during the networking library design round.
I’m Amit Shekhar from Outcome School, where I teach AI and Machine Learning, and Android.
Let’s get started.
Designing networking for an Android app is challenging because mobile networks are unreliable, slow, and unpredictable. Requests can fail, get delayed, or be interrupted by app lifecycle changes. On top of that, the system must handle performance, threading, caching, retries, and error handling while keeping the API simple for developers. A networking library exists to hide this complexity and provide a reliable, scalable way to communicate with backend services.
Key components to consider during a networking library design interview:
Request Config: It allows users of the library to pass a configuration object to define base URL, timeouts, headers, logging levels, retry policies, and etc.
HTTP Client: It handles low-level networking, connection pooling, timeouts, retries. The library should allow users to plug in their own HttpClient implementation if needed, while providing a default HttpClient (for example, OkHttpClient).
Request and Request Builder: It handles different HTTP methods (GET, POST, PUT, HEAD, PATCH, DELETE) and builds requests including the URL, headers, query parameters, and body.
Request Validation: It validates requests (required fields, headers, and payload size).
Response Parsing and Serialization / Deserialization: It converts raw network responses (JSON/XML) into Kotlin data classes and serializes data classes back into the request format.
Request Queue: Queues, prioritizes, and dispatches network requests, enabling request ordering, and cancellation.
Dispatcher: It controls how requests are executed by managing thread pools and concurrency limits.
Threading: Ensures network calls run on the background thread.
Error Handling Layer: Network errors, API errors, parsing errors, timeouts.
Caching Layer: It reduces network calls, improves performance, supports offline use.
Interceptors / Middleware: Logging, authentication tokens, headers, request/response modification.
Retry & Backoff Strategy: It retries failed requests with a backoff strategy to handle flaky networks gracefully.
Testing Support: Mocking and fake responses.
When you break a networking library into clear components, the design discussion becomes much simpler. Each part exists to solve a specific problem. This structured thinking is exactly what interviewers want to see. And if you can explain how a request flows through the system and cover all the edge cases, you’re already ahead in system design interviews.
I teach these types of concepts at Outcome School and help you become a better software engineer.
Thanks
Amit Shekhar
Founder, Outcome School