Project Overview
A high-performance enterprise cloud storage and real-time synchronization platform developed with Flutter & Dart across 4 major operating systems: Windows, macOS, iOS, and Android. To achieve 60/120 FPS native desktop & mobile smoothness, the engineering team decoupled all heavy compute (SHA-256 chunk hashing, file indexing) onto background Dart Isolates and custom-built native OS bridges : integrating Win32 System Tray, macOS FSEvents Menu Bar, iOS File Provider Extension, and Android Storage Access Framework (SAF) into a single, unified codebase.
Challenges & Pain Points
Multi-OS Native Hook Fragmentation
Standard cross-platform frameworks lack deep OS integration required for cloud sync: Windows needs Win32 Shell & Tray APIs, macOS requires FSEvents & App Sandbox, iOS restricts background sync, and Android enforces strict Scoped Storage (SAF).
UI Thread Freezing on Large Files
Computing cryptographic hashes (MD5/SHA-256), chunking multi-gigabyte files, and generating image/video thumbnails on the main UI thread caused noticeable micro-stutters and frame drops below 30 FPS.
Unreliable Resumable Sync on Unstable Networks
Transferring large folders over mobile 4G/5G or fluctuating Wi-Fi frequently suffered from network drops, requiring full re-uploads without granular byte-level chunk resuming.
Mobile Battery & OS Background Limits
Mobile operating systems aggressively kill background processes to save battery, terminating continuous file backup flows unless proper native background services are implemented.
Our Solution
Custom Native Bridges for Win32, macOS, iOS & Android
Engineered custom platform channels and C++ FFI bindings tailored for each OS: Win32 ReadDirectoryChangesW and Taskbar Tray for Windows; native FSEvents watcher, Menu Bar status, and Keychain for macOS; File Provider Extension (integrating directly into Apple's native Files app) for iOS; and ForegroundService with Storage Access Framework (SAF) for Android.
Dart Isolates & Worker Pools for Butter-Smooth 60/120 FPS
Offloaded all CPU-intensive workloads : chunk slicing, SHA-256 hashing, SQLite indexing, and media thumbnail generation : to background Dart Isolates and C++ worker threads. The Flutter main UI thread remains 100% dedicated to rendering, guaranteeing flawless 60/120 FPS smooth scrolling with 100,000+ files.
Resumable Chunked Transfer Engine & WebSocket Stream
Implemented an adaptive chunked sync engine with automatic byte-level resume and exponential backoff retry. Coupled with a persistent WebSocket event channel that streams real-time sync status, transfer speed, and remote file modifications instantaneously across devices.
Virtualized Grid Rendering & Smart SQLite Local Cache
Built a memory-efficient virtualized file grid with instant search filtering, folder tree caching in local SQLite, and lazy thumbnail memory recycling to maintain a tiny RAM footprint under 85MB on desktop and mobile.
Technology Stack
Project Highlights
- Unified Flutter codebase with custom native bridges for Windows (Win32), macOS (FSEvents), iOS (File Provider), and Android (SAF)
- Dart Isolates & background worker threads guaranteeing zero-lag 60/120 FPS UI performance
- Resumable byte-level chunked upload engine with WebSocket real-time progress broadcast
- Native Taskbar System Tray (Windows) & Menu Bar status widget (macOS) with real-time speed meter
- Multi-tier storage quota management (up to 500GB+) integrated with telecom VAS package billing