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Data sensing and retrieval in wireless sensor systems have a widespread application in areas such as security and surveillance monitoring, as well as command and control in battlefield situations. In query-based sensor systems, a user would issue a query with quality of service (QoS) requirements in terms of reliability and timeliness, and expect a response to be returned within the deadline. Satisfying these QoS requirements implies that fault tolerance mechanisms through redundancy will be used, which may cause the energy of the system to be quickly depleted. We develop a hop-by-hop data delivery mechanism in which we utilize "source" and "path" redundancy with the goal to satisfy application QoS requirements while maximizing the lifetime of the sensor system. When given QoS requirements of a query, we identify optimal "source" and "path" redundancy such that not only QoS requirements are satisfied, but also the lifetime of the system is prolonged. Numerical data are presented with physical interpretations given to demonstrate the feasibility of our approach.