Project Name
Ksolves Eliminates Redundant API Calls on an Android App Serving CloudFront Signed URLs
A large-enterprise EdTech platform headquartered in North America delivers video-based learning to universities, corporate training programs, and professional certification bodies through an Android app that serves media over AWS CloudFront with signed URLs carrying a fixed validity window. The app treated every URL as expired by default, generating a fresh backend round-trip every time a learner tapped content they had accessed seconds earlier in the same session. On congested campus Wi-Fi and cellular networks, that compound effect turned routine navigation into a frustrating wait, and the backend call, not the content delivery, was the actual bottleneck. Ksolves brought Android application development expertise to the problem, building a TTL-aware caching layer backed by Android Room so the app reuses valid URLs from local storage and only calls the backend when a URL has genuinely expired.
- Redundant API Calls on Every Content Access: The app made a fresh backend round-trip to generate a new CloudFront signed URL each time a learner accessed any piece of media, including content accessed seconds earlier in the same session, creating unnecessary network load on every interaction.
- No Awareness of URL Validity Windows: CloudFront signed URLs carry a defined validity period, but the app had no mechanism to track whether a previously fetched URL was still valid, so it treated every URL as expired by default and guaranteed a backend call on every access.
- Degraded Experience on Weak Networks: Campus Wi-Fi and cellular connections under load amplified the cost of every redundant call, and the loading delays learners hit navigating between content were entirely avoidable since the backend call was the actual bottleneck.
- No Local Persistence of Media Metadata: URL mappings, expiry times, and content metadata lived in memory only and got discarded on every app restart, so even content a learner had just accessed required a fresh backend call after returning to the app.
- Backend Load Disproportionate to Actual Content Changes: Signed URL generation requests hitting the backend ran far higher than the actual rate of content changes, since every UI navigation event triggered a generation call regardless of whether the underlying asset had changed at all.
Ksolves brought Android application development expertise to the problem, structuring the cache around a Repository Pattern with one governing principle: the network is a fallback, not the default.
- Android Room TTL Cache: A local Room database table stores signed URLs alongside their generation timestamp and TTL value, so every URL lookup checks the cache first, returning the stored URL immediately if it's still within its validity window and triggering a backend fetch only when the TTL has elapsed.
- Repository Pattern as the Single Data Gateway: All signed URL access routes through a repository layer that encapsulates cache-check and fetch logic, ensuring no UI component can bypass the cache and make a direct API call, eliminating the scattered backend call patterns that had built up across the codebase.
- TTL Calculation From CloudFront Expiry Headers: The cache TTL derives directly from the CloudFront URL expiry window, so the validity period in local storage matches the signed URL's actual lifetime, preventing both premature expiry and stale URL serving.
- Coroutines-Backed Async Cache Operations: All Room read and write operations run through Kotlin Coroutines on background dispatchers, keeping cache lookups and writes non-blocking so they never compete with the main thread for UI rendering.
- Background TTL Expiry Cleanup via WorkManager: A periodic WorkManager task purges expired URL records from the Room database, preventing unbounded local storage growth without requiring the learner to clear app data manually.
Technology Stack
| Category | Technology |
|---|---|
| Database | Android Room |
| Architecture | Repository Pattern |
| Platform | AWS CloudFront |
| Processing | Kotlin Coroutines |
| Infrastructure | WorkManager |
- Redundant API Calls Eliminated: The backend is now only called when a URL has genuinely expired, cutting API call volume significantly compared to the previous pattern of a call on every content navigation event.
- Content Load Time Reduced on Weak Networks: Cached URL lookups now return in milliseconds from local Room storage, eliminating network latency entirely for content that has been recently accessed.
- Backend Load Now Proportional to Content Changes: API calls now reflect genuine URL expiry events rather than navigation events, so backend load scales with TTL windows instead of how often a learner taps around the app.
- Persistent URL Metadata Across Sessions: Room persistence means valid URLs survive app restarts, so learners returning to recently accessed content no longer trigger a backend call just by reopening the app.
“The change was immediately visible on campus. Learners who were used to waiting for content to load were suddenly navigating without delays, and we had not changed the content delivery infrastructure at all. The fix was entirely on the client side.”
– VP Engineering, EdTech
This Android app made a backend round-trip for every CloudFront signed URL access, treating every URL as expired by default and generating redundant API calls on every content navigation event. Ksolves built a TTL-aware Room cache with a Repository Pattern gate so valid URLs now serve from local storage in milliseconds, and the backend only gets called when a URL has genuinely expired.
Content load time improvements were most pronounced on weak networks, campus Wi-Fi and cellular connections where every eliminated backend call translated directly into a faster learner experience. Backend load is now proportional to content change frequency instead of UI navigation frequency, so infrastructure cost scales with actual business activity rather than tap rate.
The same Room, TTL, and Repository Pattern combination is directly reusable for any Android app serving signed-URL media at scale; video platforms, music streaming, e-commerce, and social apps all face this exact same pattern.
Is Your Android App Making Unnecessary Backend Calls for Content Your Users Just Accessed?
