"Rapid" is relative. Using sockets is an obvious mechanism, and Datagram (UCP) type are the fastest, but stream sockets (TCP) are generally easier to synchronise. Which mechanism depends on other factors as well, like volumes and security.
You should also consider what happens when two requests for a banana come in when there is only one left. Each client will be told there is one banana, yet one must fail. Maybe transaction handling is what you mean by database design.