A few comments first:
- This looks more like functional decomposition rather than DFD: there are no flows as such.
- The breakdown between
Customer Service and
Data Service is unclear. On one hand, you have authentication listed on the left, on another
Desktop App (which presumably includes authentication) is on the right.
If you're decomposing based on function, rather than deployment (client vs. server side), then the top-level entities could look like this:
- Registration and Authentication
- File management
- Integration to client apps (Mobile/email/browser)
- Notification/event system
- Multi-user collaboration: sharing etc.
There's of course more, but that's a start.
If you're decomposing based on deployment or going for a classic DFD, then the top list would start with client-/server-side, and then for the server side, go into file storage (including CDN), NoSQL DB (also including scalability), API etc. etc.
As the comment above says, it really depends on how far you want to go.