We have a new post up on the Cesium blog by @Ankit_Trehan that takes a technical deep dive into the architecture behind Cesium ion, including API server, tiling, asset hosting, and front end.
In a follow up post, @Ankit_Trehan covers the architecture of Cesium ion Self-Hosted, which uses Kubernetes, as well as a comparison between the structure of Cesium ion Self-Hosted and Cesium ion SaaS.