Podcasts · Whiteboard Confidential
Build a Photo Sharing App for Up to 1 Billion Users: System Design Interview with a FAANG Engineer
· 1 h 01 min
Episode Build a Photo Sharing App for Up to 1 Billion Users: System Design Interview with a FAANG Engineer
REPLAY EPISODE: Curious how to approach large-scale design interviews? This is the level of depth, structure, and clarity that top companies like Stripe and Meta are actively looking for.
In this mock system design interview, a senior engineer is asked to design a photo-sharing app (something like Instagram, but from scratch and at massive scale). What follows is a masterclass in thoughtful architecture: from exploring nuanced functional and nonfunctional requirements to tackling schema design, RESTful APIs, and infrastructure choices under realistic constraints.
The candidate works through challenges like privacy controls, feed generation, follow request flows, and media storage for 1 billion daily active users—all while communicating clearly and methodically. You’ll see them navigate trade-offs around consistency vs. availability, break down how to serve images efficiently with CDNs, and set up queues for asynchronous photo processing.
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Timestamps:
00:00 Introduction
00:58 Interview Begins
02:00 Clarifying assumptions: privacy, authentication, feeds
06:45 Discussing follow requests and celebrity suggestions
09:00 Metadata and interaction features (likes, comments)
12:00 Non-functional requirements and scale (1B DAUs!)
15:00 Schema design begins: Users and Follows
20:00 Designing the Photo entity (metadata, location, blob storage)
27:00 Comment schema + verified users
31:00 Designing upload & metadata API endpoints
35:45 Designing follow request and response APIs
41:00 Designing the user’s feed + pagination
44:00 High-level architecture begins: services, DBs, queues
48:00 Document store vs. relational DB for photo storage
52:00 Serving photos via CDN + Follow service interaction
56:00 Final review and detailed feedback from interviewer
01:00:00 Encouragement on focusing more on requirements depth
Links in the notes 3
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