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Client Caching and Offline Persistence Questions

Client side caching and local data persistence strategies for applications, including in memory caches, disk based caches, and mobile platform storage options. Cover offline first design patterns where apps remain usable without network connectivity, synchronization and conflict resolution protocols for syncing local changes back to servers, eventual consistency and freshness trade offs, schema migrations and versioning for local stores, pagination and handling large data sets under device constraints, and platform specific considerations such as iOS (UserDefaults, Core Data, Realm, NSCache) and Android (SharedPreferences, SQLite, Room, Realm). Also include strategies for synchronizing state across views and components, background sync, and strategies to minimize data loss and reduce sync conflicts.

HardSystem Design
71 practiced
Design a robust schema versioning and migration strategy for mobile local stores (SQLite/Room, Core Data, Realm) that must support users upgrading from many historical app versions. Describe migration ordering, backward/forward compatibility, migration scripts, incremental migration, and techniques for testing migrations at scale.
MediumTechnical
97 practiced
In a React Native app using Redux for global state, describe a robust strategy to persist Redux state locally and keep it synchronized with remote server state. Discuss libraries (redux-persist), conflict resolution, rehydration ordering, partial rehydration, and how to avoid exposing stale/conflicting state to UI after app launch.
EasyTechnical
92 practiced
Describe common cache eviction policies (LRU, LFU, FIFO). For each policy give a concrete mobile example where it makes sense (e.g., image caches, session caches), and explain how device memory constraints and app process lifecycle influence which policy you choose.
EasyTechnical
88 practiced
How would you securely persist sensitive items such as OAuth tokens or encryption keys on Android and iOS? Discuss platform APIs (iOS Keychain, Secure Enclave, Android Keystore / EncryptedSharedPreferences), best practices for key derivation and storage, and considerations for backups and restore.
HardTechnical
69 practiced
Design secure offline storage for sensitive personally identifiable information (PII) on iOS and Android. Cover encryption-at-rest approaches, key management (Keychain / Keystore / Secure Enclave), biometric unlocking, key rotation, encrypted backups, and how to allow selective server-side recovery while preserving user privacy.

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