Building robust React applications requires understanding client-side architecture basics. The Apollo Client plays a crucial role in managing state, networking, and data fetching concerns. A better client-side architecture starting point involves using CQS (Command Query Separation) and SoC (Separation of Concerns). Presentation components should render UI and create user events, while container components connect user events to the interaction layer. The interaction layer handles model behavior and shared component state. Apollo Client is a state management library that handles storage, updates, and reactivity, including remote and client-only local state. By understanding these principles and types of state, developers can design robust and maintainable React applications.