1. An apparatus for processing a query for a NoSQL database, the apparatus comprising: a storage unit configured to store (i) a plurality of safe elements committed and saved in the database, and (ii) a plurality of unsafe elements for updating the plurality of safe elements, wherein the unsafe elements are not committed or committed, but not saved; a first query executing unit configured to execute the query on the plurality of unsafe elements; a second query executing unit configured to execute the query on the plurality of safe elements after the first query executing unit executes the query; and a third query executing unit configured to execute the query on at least one safe element saved during execution of the query by the second query executing unit after the second query executing unit executes the query.