They don't persist any state between requests from the client. i.e. the service doesn't know, nor care, that a subsequent request came from client that has/hasn't made a previous request. Basically, its a 'give me this piece of info and forget about me' which puts the onus on the client to maintain any state.
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
