Design Dropbox
PremiumProduct architectureMedium
- File sync
- Block chunking
- Content hashing
Quick answer
This product architecture interview question asks you to design Dropbox. Aim for a design that meets its requirements at the stated scale, then explain its main components, data flow and trade-offs. Interviewers want to see how you scope the problem, size it and defend each choice.
The problem
Design Dropbox, a file sync service that keeps a folder identical on a user's laptop, phone and the web, and lets people share folders. The hard parts are uploading only the changed parts of large files, telling every device about a change within seconds, and handling two devices editing the same file.
What must the system do?
- Upload changes: A file saved in the synced folder uploads automatically; after a small edit to a big file, only the changed blocks are sent.
- Sync to devices: Every other online device of the user, and of anyone sharing the folder, gets the change within 10 seconds.
How well must it do it?
- No data loss: Once a file shows as synced, its contents are never lost or corrupted; every block is checked against its hash.
- Bandwidth efficient: Small edits upload little data, and identical blocks are stored once.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- File sync
- Block chunking
- Content hashing
- Deduplication
- Long polling
- Conflict resolution
How you’ll practise
- Requirements
- Core entities
- API design
- Client and server flow
- Scale and edge cases
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any product architecture design round.
- Clarifies the requirements before drawing anything
- Uses a few numbers that actually change the design
- Draws a clear path from the client to storage
- Picks storage and caching with reasons, not by habit
- Explains what breaks first under load and how to fix it
- States trade-offs openly instead of claiming a perfect design
Questions people ask about this interview question
- Which design type is this question?
- It is a product architecture question. You design Dropbox and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Medium. Entry-level engineers can practise it, but it expects you to reason about requirements and trade-offs, not only list components.
- What should I cover first?
- Start with the requirements: what the system must do, how well it must do it and which numbers change the design. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
Related questions
Updated · Written by the SevyDevy team