Design a photo backup app like Google Photos
PremiumMobile systemMedium
- Background upload
- Resumable chunked upload
- Content hash deduplication
Quick answer
This mobile system interview question asks you to design a photo backup app like Google Photos. 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 a photo backup app like Google Photos for iOS and Android. It uploads every new photo and video from the phone's library to the cloud without the user keeping the app open. The hard parts are the OS limits on background work, resuming large uploads and never uploading the same item twice or missing one.
The storage service is a given API. Design the app: finding new media, the upload queue, scheduling and the user controls.
What must a photo backup app like Google Photos do?
- Auto backup: New photos and videos are uploaded automatically, usually within a few hours, without opening the app.
- First backup: An existing library of 10,000 items is uploaded over several days if needed, with clear progress.
How well must it do it?
- Complete and exact: Every item is backed up once; nothing is missed and nothing is uploaded twice, even after reinstalls.
- Resumable: A dropped connection loses at most one chunk of progress.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Background upload
- Resumable chunked upload
- Content hash deduplication
- PhotoKit persistent changes
- MediaStore generation
- WorkManager constraints
How you’ll practise
- Requirements
- App architecture
- Data and offline sync
- Networking and push
- Performance, battery and releases
- 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 mobile system 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 mobile system question. You design a photo backup app like Google Photos 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.
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Updated · Written by the SevyDevy team