This text discusses implementing isolated application environments in Neon, where each customer has their own copy of the entire system. The reasons for considering this approach include geographical and political requirements, ability to dictate the pace of upgrades, and tailoring the application or database to individual customers. Designing for isolated environments involves managing provisioning, deployment, capacity limits, enabled features, and control planes. Managing isolated environments requires strict discipline in software development lifecycle and maintaining a central control plane and catalog database.