Walk through the tech stack behind a video streaming app, from encoding to playback
Company: Stripe
Role: Product Manager
Category: System Design
Difficulty: medium
Interview Round: Other
You are interviewing for a product manager role and get a technical question: what technologies does it take to build a video streaming app? Explain the main pieces a streaming service needs to get a video from its source onto a viewer's screen, and name the technologies typically used for each piece, across both the backend and the apps people watch on.
```hint Follow one video
Trace a single title from the moment it arrives at the service to the moment it starts playing on a phone. Every hand-off along that path is a layer with its own technology choices.
```
### Clarifying Questions
- Is the service on-demand (a library of shows and films), live (sports, concerts, creators), or both?
- Which devices must it support: web browsers, iOS and Android phones, smart TVs and streaming sticks?
- Is the content licensed from studios, which usually requires copy protection, or uploaded by users?
- Should the answer cover what the team would build itself versus buy from cloud and video-platform vendors?
### What a Strong Answer Covers
- An end-to-end architecture in a sensible order: ingest, encoding, packaging, storage, delivery and playback.
- Concrete technologies at each layer (codecs, streaming protocols, DRM, CDNs, player libraries) with the reason each is used, rather than a list of names.
- The application layer around the video: backend services, data stores, accounts and payments, analytics and recommendations.
- How the choices change between on-demand and live streaming, especially for latency.
- A product manager's lens on the stack: build versus buy, the main cost drivers, device coverage and playback-quality metrics.
### Follow-up Questions
- How would the stack change to stream a live sports match with only a few seconds of delay?
- Delivery bandwidth is usually the largest cost line. Which levers would you pull to cut it without visibly hurting picture quality?
- Which playback-quality metrics would you put on the team's dashboard, and why?
Overview: A technical question for product managers that asks you to explain the technologies behind a video streaming app. It tests whether you can trace a video from ingest to playback, name the main tools at each layer of the stack, and reason about build-versus-buy, cost and live-versus-on-demand trade-offs.