TL;DR — Dropbox File Sync

Design a cloud file synchronization service like Dropbox that keeps files in sync across multiple devices. Users install a desktop client that monitors a local folder, detects file changes, and uploads them to the cloud. Other devices running the same client receive the changes and apply them locally, keeping all devices in sync. Key features: Auto-sync files across all linked devices. Block-level chunking with 4MB default chunk size.