A Keras developer designs, builds, and deploys machine learning models using the Keras Python library. They leverage Keras' user-friendly and modular architecture to prototype and implement deep learning algorithms swiftly. Their tasks include data preprocessing, defining model architecture, configuring learning process, and training models. They also optimize models for improved performance and accuracy. Their role involves assessing model performance using appropriate metrics and visualization tools. Moreover, they collaborate with data scientists and engineers to integrate models into larger systems and applications. They continuously stay updated with the latest advancements in AI and machine learning.