APIs, Networking & Integration Topics
API design, management, and integration patterns including REST, GraphQL, and other protocols. Covers API contract design, versioning strategies, error handling, idempotency, deprecation planning, and SDK/integration frameworks. Includes system-to-system integration, webhook patterns, and integration platform considerations. Excludes network infrastructure and network-layer protocols (see Network Architecture under Cloud & Infrastructure or a dedicated networking category if needed).
API Integration and System Connectivity
Covers the end to end concepts and practices for connecting systems using application programming interfaces and integration middleware. Candidates should understand REST and HTTP fundamentals, webhooks versus polling, API authentication and authorization patterns, request and response formats, rate limiting, versioning, and reading API documentation. Include practical skills for building and troubleshooting integrations: data mapping and transformation, schema mapping, message formats, error handling and retry strategies, idempotency, logging and monitoring, and ensuring data consistency across synchronous and asynchronous flows. Also includes integration tooling and middleware platforms, real time versus batch synchronization, designing for partial failures and back pressure, and frontend concerns such as async data fetching, loading and error states, pagination, optimistic updates, and race condition mitigation.
Client Performance and Networking
Covers concurrency and performance optimization for client applications, especially mobile and desktop apps. Topics include high level concurrency primitives and patterns such as Grand Central Dispatch, async and await, coroutines, thread safety, race condition prevention, deadlock avoidance, and testing for concurrency bugs. Networking topics include HTTP best practices, connection management, retry and backoff strategies, efficient request serialization, error handling, and use of standard networking libraries and frameworks. Performance concerns include application launch time reduction, memory footprint management, responsiveness and frame rate stability, battery and energy efficiency, and strategies for reducing networking cost and latency. Tooling and measurement include profiling and tracing techniques, using platform profilers and instruments for CPU, memory, and network analysis, capturing and interpreting performance traces, and identifying hotspots to guide optimization efforts. Candidates should be able to explain trade offs between responsiveness, resource usage, and code complexity and propose concrete optimizations and measurement approaches for client scenarios.
API Integration and Networking
Making and managing network requests to external services and third party APIs, including HTTP fundamentals and REST principles. Topics include constructing requests, headers and authentication schemes such as token handling and refresh flows, parsing and serializing JSON, handling HTTP status codes, network error handling, timeout and retry strategies, backoff, offline and caching strategies, security concerns such as HTTPS and certificate pinning, and familiarity with common networking libraries on different platforms. Candidates should demonstrate the ability to integrate external APIs reliably and securely and to reason about networking trade offs.
Data Management and Api Design
Designing how applications structure, expose, and consume data through APIs and backend systems. Covers API design principles for data endpoints, pagination, filtering and sorting, idempotency, versioning, rate limiting, schema design, normalization versus denormalization, consistency models, caching strategies, client side fetching patterns, and error handling. Includes considerations for data integrity across integrations, transactional boundaries, master data management, and how API decisions affect downstream consumers and performance.
Mobile Networking and API Integration
Covers the design and implementation of network communication between mobile clients and backend services. Core protocol knowledge including Hypertext Transfer Protocol and secure Hypertext Transfer Protocol, representational state transfer principles, request and response serialization such as JavaScript Object Notation and protocol buffers, and API patterns suitable for mobile consumption. Platform specific implementation details including Apple iOS networking stacks and libraries such as URLSession, Android libraries such as OkHttp and Retrofit, and cross platform considerations. Reliability and resilience topics including network connectivity change handling, connection pooling, retry strategies and exponential backoff, timeout management, interceptors and middleware, circuit breaker and rate limiting patterns, and error classification and recovery. Performance and efficiency topics including request batching, compression, payload size reduction, caching strategies, cache invalidation, offline first approaches, local data storage and synchronization, conflict resolution strategies, and optimization for bandwidth constrained networks. Security and authentication including Transport Layer Security and certificate pinning, secure sockets layer considerations, token based authentication and refresh flows including Open Authorization and JSON Web Tokens, secure storage of credentials, and certificate and key management. Testing, debugging and observability including network mocking and stubbing, integration testing strategies, logging and telemetry for network flows, monitoring for latency and error rates, and handling of streaming and real time channels such as WebSocket and long polling when applicable.
Backend API Design for Mobile Clients
Designing backend application programming interfaces specifically for mobile clients, addressing mobile device constraints, network variability, and cross platform compatibility. Core concerns include bandwidth optimization techniques such as pagination, selective field queries, delta responses, efficient serialization formats, and compression; response shape and protocol trade offs including representational state transfer versus GraphQL; versioning and backward compatibility strategies for long lived mobile applications; error handling, retry semantics, and user friendly error surfaces appropriate for intermittent connectivity; rate limiting, throttling, and quota management; real time synchronization patterns including polling, web sockets, and server sent events; caching, offline support, data synchronization, conflict resolution, and optimistic updates; authentication and token refresh strategies, security and privacy considerations; and monitoring, telemetry, testing, and deployment practices that minimize breaking changes for mobile clients.
Real Time Data and WebSocket Integration
Design and implement real time experiences that keep frontend state synchronized with backend changes. Topics include WebSocket and server sent event options, connection lifecycle and reconnection strategies with backoff and jitter, heartbeats and health checks, message ordering and idempotency, batching and backpressure management, optimistic UI updates and conflict resolution, authentication and security for persistent connections, and testing and observability for real time systems. Candidates should discuss trade offs between latency, reliability, complexity, and server cost.
API Design and Data Fetching Strategies
End to end design and client side integration of data APIs and fetching strategies. On the server side consider representational state transfer design principles, GraphQL schema and query trade offs, endpoint versioning, pagination approaches, batching, idempotency, and error semantics. On the client side cover pagination and incremental loading, request cancellation and abort semantics, debouncing and throttling, retry strategies and exponential backoff, optimistic updates, loading and error state management, and client side caching patterns such as stale while revalidate. Also include real time synchronization options such as WebSockets and server sent events, offline first synchronization and conflict resolution, service worker integration, and security considerations for authentication and authorization.
Third Party Service Integration
Designing and implementing integrations with external services and software development kits in mobile applications. Core areas include secure payment gateway integration, analytics and crash reporting providers, social login and OAuth flows, remote configuration and attribution SDKs, handling webhooks and callbacks, dependency and version management for third party libraries, startup and initialization impacts, privacy and data handling compliance, testing and mocking third party behavior, and designing graceful degradation and retry strategies for unreliable external services. Interviewers probe for patterns to isolate, test, and mitigate risks introduced by third party dependencies.