Capacitor Storage or WebView localStorage: Which to Use for Low‑Latency Key/Value Persistence?

Key/Value Persistence in Capacitor Apps

The goal is to store small, frequently accessed key/value pairs in a Capacitor 5.x application while keeping the UI thread responsive and ensuring data security across iOS and Android.

Two documented approaches are available:

• Capacitor Storage plugin – uses SQLite on iOS and SharedPreferences on Android, offers an async API, and can encrypt data with the optional encrypted: true flag.
• WebView localStorage – synchronous access within the WebView, limited by the browser engine’s quota, and no built‑in encryption.

Key constraints include:

• Performance – async storage should avoid UI jank compared to synchronous localStorage.
• Security – encryption support in Capacitor Storage versus plain text storage in localStorage.
• Platform consistency – Capacitor Storage’s API is stable across releases, whereas localStorage behavior may vary with WebView updates.

Given these factors, which approach best balances low UI latency, data protection, and cross‑platform reliability for small key/value data?

Questions

1. How does Capacitor Storage’s async API affect UI responsiveness compared to synchronous localStorage when performing 1,000 write operations?
2. Does enabling encrypted: true in Capacitor Storage guarantee that the stored data remains inaccessible to the WebView’s localStorage?
3. Will Capacitor Storage maintain consistent behavior across future Capacitor releases while localStorage may change with WebView updates?