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We implemented a generalized infrastructure for Internet of Things (IoT infrastructure) to be applicable in various areas such as Smart Grid. That IoT infrastructure has two methods to store sensor data. They commonly have the features of double overlay structure, virtualization of sensors, composite services as federation using publisher/subscriber. And they are implemented as synthesizing the elemental architectures. The two methods majorly have the common architectural elements, however there are differences in how to compose and utilize them. But we observed the non-negligible differences in their achieved performance by the actual implementations due to operational items beyond these architectural elements. In this paper, we present the results of our analysis about the factors of the revealed differences based on the measured performance. In particular, it is clarified that a negative side effect due to combining independent elemental micro solutions naively could be amplified, if maximizing the level of loose coupling is applied as the most prioritized design and operational policy. Primarily, these combinations should be evaluated and verified during the basic design phase. However, the variation of how to synthesize them tends to be a blind spot when adopting the multiple independent architectural elements commonly. As a practical suggestion from this case, the emphasized importance in carrying out a new synthetization with multiple architectures is to make a balance naturally among architectural elements, or solutions based on them, and there is a certain demand to establish a methodology for architectural synthetization, including verification.