A multinational client wants to hire you for the development of a high availability system for their new business, they want to avoid single vendor lock in and develop a system which is not dependent on a single database engine $($DBE$),$ As a seasoned developer you are asked to implement an n$-$tier system with different database engines access from the dafa$-$tier of this system, without exposing the details of the DBE to the client system code in java. Analyze the best practice and design patterns possible to have this implementation feasible for the client by giving them the correct implementable piece of code. $66$ marks