Providing quality-of-service guarantees for data services in a distributed environment is a challenging task. The presence of multiple sites in distributed environments raises issues that are not present in centralized systems. The transaction workloads in distributed real-time databases may not be balanced and the transaction access patterns may be time-varying and skewed. Data replication is an effective method to help database systems meet the stringent temporal requirements of real-time applications. We have designed an algorithm that provides quality-of-service guarantees for data services in distributed real-time databases with full replication of temporal data. The algorithm consists of heuristic feedback-based local controllers and global load balancers (GLB) working at each site. The local controller controls the admission process of incoming transactions. The global load balancers collect the performance data from other nodes and balance the system-wide workload. The simulation results show that the new algorithm successfully balances the workloads in distributed real-time databases and provides tight transaction miss ratio guarantees under various transaction workloads.