A CAP Theorem developer designs and manages distributed systems, ensuring they effectively balance between Consistency, Availability, and Partition Tolerance (CAP). They understand that a system can't simultaneously provide all three aspects perfectly, thus they make strategic trade-offs based on specific application needs. They might prioritize consistency for financial systems or availability for social media platforms. They also focus on system resilience during network failures, ensuring optimal partition tolerance. Their work involves continuous system monitoring, problem-solving, and refining system design to optimize performance. They also collaborate with other developers, sharing insights about managing distributed data systems.