Using a data page with a predefined key enhances performance by leveraging the caching mechanism of Pega. When a data page is loaded with a specific key, it is stored in memory. Subsequent accesses to the data page with the same key do not require fetching the data again from the external data source, significantly reducing the access time. This approach is particularly beneficial in cloud deployments where network latency can impact performance. It ensures that once the data for a particular customer is fetched and stored in the cache, accessing the same customer's information again is much faster, addressing the performance issue reported.References: Pega Community documentation on data pages and performance best practices.