Dropbox

Client side

Watcher

Watches directory for added files. Send info to indexer about added files.

Indexer

Receives events about files added, deleted. Breaks down the file in chunks. Add info about file chunks to local metadata DB.

Chunker

Chunk the file by given location. 4Mb blocks.

Versioning

Server side

At first we upload blocks of file (step 4). Once it is confirmed we send a message to the queue.

This queue can be split by geo or buy other means.

Sync service

Saved metadata, makes sure that all info and file content is consistent.

Notification about file changes from Notification service can be delivered via Websocket or HTTP long polling.