> I wanted to know if there was a lot of magic that happens in the backend sdk ? There is indeed a lot happening in the backend SDK. > If i end up needing to read an SDK which one do you think will be the best ? You can read the supertokens-node one. > As I understand currently the backend SDK provides a set of http endpoints and translate it for the core to understand Yes. So those endpoints exposed by the backend SDK (via a middleware) are called by the frontend. In turn the backend SDK calls the core. The backend SDK also does input normalisation and sanitisation + reading and setting cookies whenever needed. For effeciency purpose, the backend SDK also does stateless session verification.