System designHardsd-g258

Subject Image processingLevel Senior–Staff~45 minCommon in Distributed systems interviewsIndustries Technology, Software development

Question

Design the real-time camera-filter / AR-effects system for a social app where users apply face-tracking lenses and effects live in the camera preview at 30fps on a wide range of phones, and the same effect must render consistently when applied to a captured photo/video server-side (for users on devices too weak to run it live). Effect creators publish new lenses constantly. Design the runtime, the effect distribution, and how you reconcile on-device real-time with server-side rendering.

What a strong answer looks like

Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts — data model, bottlenecks, consistency, failure modes — and name the trade-offs you are making.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.