1. A method for making an admission control decision in a cloud database system, the method comprising: systematically predicting a probability of a candidate query to be finished before a deadline; admitting or rejecting the candidate query to the cloud database system based on probabilities for queries to meet query deadlines and based on profits of different SLA based decisions; for a query q, if the query q is admitted and meet a deadline τ, obtaining a profit gain of q; else if the query q miss the deadline τ, paying a penalty −p; and rejecting the query q up-front and paying a reduced penalty of −r where r<p.