Server-side ad insertion

Design server-side ad insertion (SSAI) for an ad-supported streaming service that stitches personalized ads into the video stream at the manifest/segment level so the ads can't be blocked and play seamlessly (no buffering at the ad boundary). Each viewer gets different ads (targeting), so you can't serve one shared manifest; you must decide ad breaks, call an ad decisioning service per viewer, splice ad segments into the content timeline, and track that ads were actually watched, for live and VOD, at millions of concurrent streams.