We propose T-DHT, a hybrid unstructuredstructured DHT based approach, to cope with the high demanding requirements of social applications, in a fully scalable, distributed and balanced way. T-DHT behaves as a structured DHT when publishing "tag, social-object" associations, and as an unstructured filter driven network when searching for the socialobjects by means of any tag combination. The publishing process stores tag information across node links in order to drive adequately the later search operations in at most O(Log(N)). The search process takes at most O(logN) node hops for any tag combination and uses the previously stored node link tag information.

Although T-DHT has been devised to build a scalable social application infrastructure, it can also be applied to solve general Peer-to-Peer keyword search problems.