XState is a library for creating, interpreting, and executing finite state machines and statecharts in JavaScript and TypeScript. It helps developers model state logic explicitly, making complex app behaviors easier to manage, debug, and test.

Server-sent events, unlike WebSockets, are unidirectional; that is, data packets are transmitted from the server to the client (such as a user's web browser). This makes them a good alternative when data from the client to the server does not need to be sent in message form.

Cross-Site Request Forgery (CSRF) is a type of attack that causes an authorized user to do undesirable activities on a web application. An attacker can deceive users of a web application into doing activities of the attacker's choosing using social engineering techniques.