how to share a common data structure in high performance java web service applications
===

I am developing a couple of web services - one to BUY a product and other VALIDATE a product. Multiple clients will be calling the BUY (around 250/sec) and same for VALIDATE. 
They need to query and update a tabular data structure before calling the backend. 

I have a feeling using a relational database table like Oracle etc to maintain this common data structure will slow down things coz of network latency (assuming database and queries are tuned optimally).. I have been proposed EhCache and Hazelcast .. but I prefer using a database table coz I know it better.. Can anyone confirm if hitting a database across a network could prove to be a bottleneck for an application that's supposed to serve 250-300 transactions per second.  Certainly we are okay if the server instance goes down and we lose the in-memory represenation of the data structure.. 

ALso the table won't contain too many rows.. something like 5000 rows and a given select won't return more than 10 rows and a given update won't update more than 5 rows. 