I am trying to reduce amount of indexes (I want to remove all xdb, fxm, marketing indexes), but sitecore documentation is not helpful with it.
I created patch to disable Xdb and Tracking and to delete marketing indexes from configuration, but Content Editor stopped working after deletion of indexes.
Also I added
<add key="exmEnabled:define" value="no" /> in Web.config
There was a detailed answer for Sitecore 8: How to disable xDB related search indexes, when using CMS-only mode?
Maybe someone has such manual for Sitecore 9, because structure of configs was changed a lot.