> Backend – a headless service that does the heavy lifting: indexing, static analysis, advanced search, navigation, and the like. Every such operation is initiated by a request from the workspace, which then processes the response and dispatches the data to the components that require it.

> As a backend, you can use a headless IntelliJ IDEA or a language server.

https://www.jetbrains.com/help/fleet/architecture-overview.h...