Design Instagram
PremiumProduct architectureEasy
- Photo upload
- Pre signed URLs
- CDN
Quick answer
This product architecture interview question asks you to design Instagram. 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 Instagram, a photo-sharing app where people post photos, follow other accounts and scroll a home feed of new posts from the people they follow. The hard parts are storing and serving billions of images cheaply and loading the feed fast when some accounts have 100 million followers.
What must the system do?
- Post a photo: A user uploads one photo (up to 20 MB) with a caption; it appears in followers' feeds within a minute.
- Home feed: A user scrolls posts from accounts they follow, newest first, 20 posts per page, with infinite scroll.
How well must it do it?
- Fast feed: The first feed page returns in under 500 ms at p99, and images start showing within 1 second on a 4G phone.
- No lost posts: Once the app says a post is shared, the photo and caption are never lost.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- Photo upload
- Pre signed URLs
- CDN
- Feed fan out
- Follow graph
- Object storage
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 Instagram and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Easy, so it suits engineers who are new to product architecture interviews. It is also a good warm-up before harder questions.
- 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