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Storage types

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Storage Types Deep Dive

Overview

Android offers multiple storage options with different security, structure, and sharing behavior. Choosing the right one is a common interview topic.

Storage Options

SharedPreferences / DataStore

  • Key-value preferences.
  • Best for flags/settings.
  • For modern apps, prefer DataStore over legacy preferences APIs.

Internal Storage

  • App-private files.
  • Removed on uninstall.
  • Good for private cached or persisted files.

External/Scoped Storage

  • Shared media/documents model.
  • Scoped storage rules apply on modern Android.
  • Use MediaStore / SAF depending on use case.

Room/SQLite

  • Structured relational data.
  • Queryable and transactional.
  • Best for offline-first and complex domain models.

Cache Directories

  • Temporary, reclaimable by system.
  • Never store critical data only in cache.

Selection Guide

  • Settings -> DataStore/SharedPreferences
  • Structured domain data -> Room
  • User-visible media -> MediaStore
  • Temporary payloads -> Cache

Interview Traps

  • Assuming external storage is always globally readable/writable.
  • Storing large structured data in preferences.
  • Ignoring migration/backup strategy.

Key Takeaways

  • Match storage choice to data lifetime and access pattern.
  • Prefer modern APIs (Room, DataStore, scoped media APIs).