Query performance drivers

Query performance is driven by:

• Number of unique values per (indexed) attribute
• Number of indexed attributes in navigation index (see treebuilder.log or navigation index BM page)
• Number of fields in use in the search index and search passes
• Total number of items
• Number of synonyms applied per query
• Number of search modifications applied per ranking
• Choosing the right sort attributes, numbers are faster than text

From all the above, less is faster!

The second driver is the attribute type chosen, see:  Choosing the correct Fredhopper basetype

The order in terms of performance is: int, float, list64, set64, text, list, set, hierarchical, asset. (see: Understand Fredhopper data types (basetypes))

This blog article What are the main performance drivers of a Fredhopper Qserver ? might also be of interest.