The Internet has become increasingly important to many emerging application such as Blog, Wikis, podcasts, and others Web-based communities and social-networking services, i.e. Web 2.0. Behind the scenes, added functionalities depend on the ability of users to work with the data stored on servers, i.e. DBMSs. However, the unpredictability and fluctuations of requests could result in overload, which can substantially degrade the quality of service. It is a challenging task to provide quality of service with inexpensive and scalable infrastructure. In this paper, we look at a new architectural design dimension, POEMS, that is online transformable between a single-node server and peer-based service network architectures. POEMS operates as a conventional DBMS under normal load conditions and transforms to peer-to-peer operation mode for processing under heavy load. In contrast to traditional distributed DBMSs, all nodes contribute their spare capacities for data manipulation. This is achieved without the need to install any DBMS at any of the contributing nodes. Data are partitioned online and operators are distributed to nodes similarly. The effectiveness of query processing is achieved by node cooperation. POEMS allows processes or operators to be dismissed online, so a user can fully utilise his/her resources.