Develop a product recommendation engine to enhance user engagement and personalize user experiences. The engine should integrate with our existing e-commerce platform and consider user preferences, browsing history, and purchase behavior. Additionally, include backend processes to manage product catalogs, update user profiles, and generate recommendations. The solution should handle a high volume of users and be scalable to meet future growth. Ensure the engine seamlessly integrates with our frontend application using RESTful APIs. Prioritize user privacy and data security throughout the development process.