A Google Protocol Buffers developer designs and implements efficient, extensible, and scalable data structures using Protocol Buffers (protobuf), a language-neutral binary format developed by Google. They optimize communication protocols, create APIs, and manage data exchange between services, ensuring high-speed and low-overhead serialization. They convert data structures to protobuf format, reducing data size for network transmission or storage. Their role also involves ensuring compatibility with multiple languages and platforms. They collaborate with other developers, contribute to system design, and troubleshoot any issues related to data serialization or deserialization.