Context

API integration is a core part of mobile engineering because most apps depend on remote services for authentication, content, payments, and synchronization. Interviewers use this topic to evaluate whether you understand both client-side implementation details and system-level trade-offs.

Core Question

Describe your experience with integrating APIs in mobile applications. In your answer, explain:

1. how a mobile app sends requests, parses responses, and updates UI state,
2. how you handle failures such as timeouts, retries, rate limits, and offline mode,
3. how you approach authentication, security, caching, and versioning.

Scope Guidance

The interviewer is not looking for a personal story alone. They expect a structured technical explanation of the request lifecycle, common implementation patterns, and practical trade-offs. You should be able to discuss both the happy path and failure cases, and mention how you would design the integration to be reliable, maintainable, and responsive on a resource-constrained client.

Request Lifecycle

A mobile app typically builds an HTTP request, sends it asynchronously, receives a response, validates status codes, parses JSON, and maps the result into app models. The final step is updating UI state in a way that keeps loading, success, and error states explicit.

response = client.get(url)
if response.status_code == 200:
    data = parse_json(response.text)
    state = {"status": "success", "data": data}

Asynchronous Networking

Network calls must not block the main UI thread because mobile apps need to remain responsive during slow or unreliable connections. Async execution, callbacks, futures, or coroutines are used so the app can continue rendering while requests are in flight.

async def fetch_profile(client, url):
    response = await client.get(url)
    return response

Error Handling and Resilience

Good API integration distinguishes transport errors, server errors, client errors, and parsing failures. Retry logic, exponential backoff, request cancellation, and fallback behavior improve reliability without overwhelming the backend.

for attempt in range(3):
    try:
        return send_request()
    except TimeoutError:
        wait(2 ** attempt)

Caching and Offline Support

Caching reduces latency, bandwidth use, and repeated server calls. Mobile apps often combine in-memory cache for fast reads with persistent local storage so users can still see recent data when offline.

if key in memory_cache:
    return memory_cache[key]
if key in disk_cache:
    return disk_cache[key]

Authentication and Security

Mobile clients commonly use token-based authentication such as OAuth or JWT-based flows. Sensitive tokens should be stored securely, requests should use HTTPS, and the app should avoid exposing secrets or trusting client-side validation alone.

headers = {"Authorization": f"Bearer {token}"}
response = client.get(url, headers=headers)