Hiring an Apache Zookeeper developer can greatly enhance your system's reliability. Zookeeper is a distributed coordination service that manages large sets of data and services. A developer proficient in it can ensure high availability and resilience of your application, manage configuration information, and provide distributed synchronization. They can handle failures and maintain consistency across nodes, which is crucial for complex, distributed applications. They can help build robust systems, reducing downtime and enhancing user experience. Their expertise could be a valuable asset in managing your distributed systems effectively.