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Client-Server Architecture is assumed when working with web APIs, so we won't explore this. The Cacheability and Layered System constraints are generally handled through intermediary devices between the client and the server as a way of improving performance and reliability, so we won't explore these either. Finally, Code on Demand is an optional constraint that is only useful in environments where the client and the server are tightly controlled. Therefore we'll skip over this as well. This leaves us to explore Statelessness and Uniform Interface.

Statelessness

A stateless system is one where the server is unaware of the state of the client. That is, the server makes no assumptions about what data the client already has or what options are available to the client. In systems where the client state is managed (i.e., a stateful design), this is often handled through session managers, which are server-side systems that track the activity of each client. REST maintains that stateful designs will eventually become over burdened and hinder scalability.

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