Use this key in geomsearch.cfg to configure the use of GeoDb in Web API:

[settings]
#:VALS_M;"0","1";"No","Yes"
#:HELP;Uses the new search methods via GeoDb for color and partial search in the web API
UseGeoDbSearchInWebApi=1

Default is to use GeoDb. Topo search is always done with GeoDb, there is no support for the old index.