Design a video-on-demand streaming service
Company: Roku
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Onsite
## Scenario
Design a large-scale **video-on-demand (VOD) streaming service** similar to a major streaming platform.
Users should be able to:
- Sign in and browse a catalog of movies/shows
- Click a title and start playback on web/mobile/TV apps
- Seek/pause/resume and continue watching across devices
- Stream smoothly under varying network conditions
Content providers should be able to:
- Upload video assets
- Have videos processed (transcoded) into multiple qualities
- Publish titles to the catalog
## Assumptions (you can adjust during discussion)
- Global users, multi-region
- Millions of daily active users
- A typical title is hours long; streaming uses segmented adaptive bitrate
## What to cover
- Requirements (functional + non-functional)
- APIs/interfaces (high level)
- High-level architecture and core services
- Storage choices and data modeling
- CDN/edge strategy, caching, and adaptive bitrate streaming
- Transcoding pipeline
- Scalability, reliability, and observability
- Key trade-offs (latency vs. cost vs. consistency)
Quick Answer: This question evaluates a candidate's ability to design a large-scale video-on-demand streaming system, testing competencies in distributed systems architecture, scalability, CDN/edge strategy, adaptive bitrate streaming, transcoding pipelines, API and storage design, data modeling, and trade-off analysis.