The back-end of a website is a major part of your website (approximately 50%, because there's only two options (front-end and back-end)). However, querying the back-end for information can take time and effort. This delay subsequently causes the user to get frustrated which leads to terrible user experience. From this, we can derive that a back-end leads to terrible user experience.
This is where crumbsDB comes in. Instead of querying the back-end, just store your data in cookies! This minimizes the communication and increases user experience.
Additionally, replacing your database with cookies means less server costs which leads to revenue and profit. Really, this is a win-win situation which I think means it's synergy.