Code Room
System designMediumsd-g506
Subject File storageLevel Mid–Senior~40 minCommon in Storage & CDN interviewsIndustries Technology, Software development

Question

Design the origin-shield + range-request serving layer for delivering very large media files (multi-GB video masters, game installers) from a blob store through a CDN, where clients (download managers, video players) constantly issue HTTP Range requests for arbitrary byte ranges and resume interrupted downloads. The problems: a cold-popular large file triggers many overlapping range requests that all miss and stampede the origin; partial-content responses must cache correctly; and a flaky client resuming at byte 4GB must not re-download from zero. Scale: tens of Gbps egress, files up to 100GB.

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.

Narrate your design
Loading whiteboard…
Run or narrate your approach, then ask the coach.