Advertising is an integral part of premium broadcasters' and video content providers' monetization strategies. To optimize revenue opportunities, this advertising needs to be personalized accurately for the user and delivered so that it does not impair the quality of a viewer's experience. The industry is moving towards server-side advertising insertion (SSAI). With SSAI, a single uninterrupted stream containing both program and commercial content is delivered at a consistent quality, and commercials are personalized for each individual stream at the moment of delivery. This paper examines the architectures required to achieve SSAI at scale so that thousands or even millions of concurrent, individually-tailored advertising manifests can be delivered in a timely fashion, even for live streamed events. To achieve this scale, cloud and cloud-assisted software solutions are required. This paper assesses the effectiveness of this approach and the long-term practicalities of delivering targeted and secure dynamic advertising with high quality of experience.