# Flow zones overview

Three flow zones are responsible for processing transactions data, leading to items recommendations for customers:

They are the backstage of the Dataiku application [Customers rules recommendations](article:53) section. 

![recommendation_preprocessing_zones.png](SYdb53fnij8H)

Flow zones presentation:
- [recommendations_preprocessing](article:45): it contains common preprocessing steps for the two following flow zones.
- [cross_sales_recommendations](article:47): it leads to recommendations of items that customers DID NOT purchase in their last transactions.
- [repeat_purchase_recommendations](article:46):  it leads to recommendations of items that customers purchased in their last transactions.


