Middleware components are becoming increasingly important as applications share computational resources in distributed environments. One of the main challenges in such environments is to achieve scalability of concurrency control. Existing concurrency protocols lack scalability. Scalability enables resource sharing and computing with distributed objects in systems with a large number of nodes. We have designed and implemented a novel, scalable and fully decentralized middleware concurrency control protocol. Our experiments on a Linux cluster indicate that an average number of three messages is required per lock request on a system with as many as 120, which is a logarithmic asymptote. At the same time, the response time for the requests scales linearly with the increase in concurrency level. A comparison to another scalable concurrency protocol shows that our protocol results in significantly superior asymptotic savings in message overhead and response time for large number of nodes. While our approach follows the specification of general CORBA concurrency services for large-scale data and object repositories, the principles are applicable to any distributed concurrency services and transaction models. The results of this work impact scalability for distributed computing facilities ranging from embedded computing with distributed objects over peer-to-peer computing environments to arbitrating accesses in very large database environments.