End-to-End Streaming Playback: Entitlement, Manifest, DRM, CDN and Ads After Play

You are interviewing for a product manager role at Sling TV. The interviewer asks you to explain, step by step, what happens behind the scenes on a video streaming service from the moment a viewer presses play until the video is on screen, and what keeps happening while it plays. Name the systems involved and what each one does. ```hint Follow the request Trace the request in order: what must be checked before any video is sent, what the player has to learn about the stream before it can fetch anything, and where the video data actually comes from. Then cover what keeps running after the first frame appears. ``` ### Clarifying Questions - Is the viewer starting a live channel or an on-demand title? Playlist handling and ad insertion differ between the two. - Which device should I assume: a phone app, a web browser, or a smart TV or streaming stick? The device determines the streaming format and the content protection system used. - Should advertising be part of the flow, and if so, are ads stitched into the stream on the server or requested and played by the player itself? - How deep should I go: a product-level walkthrough of the services, or protocol detail such as playlist structure and the license exchange? ### What a Strong Answer Covers - The checks before playback: sign-in, entitlement to the content, and rights rules such as location, blackouts and the limit on simultaneous streams, plus what the viewer sees when one fails. - How the player discovers and fetches the stream: the manifest, multiple quality renditions, short segments served from a content delivery network, and adaptive bitrate switching. - Content protection: how the device obtains decryption keys through a license exchange without the keys being exposed. - Ad insertion and the ongoing work after the first frame, such as heartbeats, quality telemetry and saving the resume point. - A product lens on which steps drive start-up time, buffering, delay behind live and playback failures, and the trade-offs in improving them. ### Follow-up Questions - Viewers say live sports take too long to start and run well behind the broadcast. Which steps would you examine, and what would you trade off to fix each problem? - What are the product trade-offs between stitching ads into the stream on the server and having the player fetch and play ads on its own? - A viewer's subscription lapses in the middle of a show. What should happen, and which part of the system enforces it?