Java is about an order of magnitude faster than Python. It's a JIT-compiled statically typed language, after all, and Oracle's JIT compiler is the best in class

Java is about an order of magnitude faster than Python. It's a JIT-compiled statically typed language, after all, and Oracle's JIT compiler is the best in class. That said, given your original request, I don't think it has much to do with language choice. Displaying a very large number of rows in a data grid or similar is a classic GUI task in line-of-business apps, and the answer has always been either virtualization (lazy loading) or pagination. One trick to improve UX when virtualizing data is to do preloading asynchronously in the background - ideally on a separate thread - and start it before the user scrolls all the way to the end (e.g. when there's still a couple of pages of data left).