We have a lot of records in Salesforce and it is very time-consuming to rebuild all keys for a scenario before we can test the matching logic. Is there a way to test new or changed rules WITHOUT having to rebuild all the keys first?
Yes. Since keys are built/updated every time a record (Account/Contact/Lead) is inserted/updated, changes to matching (rules, object filters, account cleaning list changes etc.) can be tested WITHOUT rebuilding all keys by simply updating the existing record that should be matched, and then inserting a new "matching" record.
Once all changes have been tested THEN the keys can be rebuilt for all existing records.