Cursor Design

A cursor travels through systems the API does not control. A client may save it overnight, retry it twice, send it with different filters, or accidentally reuse it under another account. The service needs to distinguish valid continuation from a request that would change the meaning of the traversal.

Cursor design connects a public token to trusted continuation state.

This chapter develops that connection for a bookstore collection, covering boundaries, query identity, storage, protection, validation, and lifecycle decisions.