1. A method for handling data access request, comprising: receiving a semantic request submitted by a user to access data entries stored at a primary data server running a relational database management system (DBMS); decomposing the received request into logic query segments, each logic query segment having a corresponding answer set retrievable from the primary data server based on a DBMS query formulated based on the logic query segment; determining whether a corresponding answer set of a particular decomposed logic query segment is stored and ready in an in-memory data storage at the fast query service engine such that a DBMS query submission at the primary data server is obviated, the fast query service engine being different and separate from the primary data server; in response to determining that a corresponding answer set of a particular decomposed logic query segment is not stored in the in-memory data storage at the fast query service engine, formulating a DBMS query based on the particular decomposed logic query segment and fetching answer set of the particular logic query segment from the primary data server; in response to determining that a corresponding answer set of a particular decomposed logic query segment is stored but invalid in the in-memory data storage at the fast query service engine, formulating a DBMS query based on the particular decomposed logic query segment and updating contents of the answer set by synchronizing copies of data on the primary data server and in the in-memory data storage; in response to determining that the corresponding answer set of a particular decomposed logic query segment is stored and ready in the in-memory data storage at the fast query service engine, directing the logic query segment to the fast query service engine and retrieving an answer set of the particular decomposed logic query segment from the in-memory data storage at the fast query service engine; composing query results from the answer set received from the primary data server and the answer set retrieved from the in-memory data storage at the fast query service engine; and providing the composed query results to the user submitting the semantic request.