Will there be any affect to the supportability of the Service Desk product if the backend database is modified by adding additional indexes?
The support contract will not be affected at all, but it is important to note that if there is an issue where CA Support determines that the indexes are causing any problem with Service Desk, CA Support will ask to remove them. This applies to any modification made to the database that could affect the performance or the normal functionality of Service Desk.
Additional patching activities as part of software maintenance may also impact the custom indexes. As a rule of thumb, always test any changes to the backend MDB database in a non-production environment beforehand and ensure all appropriate backups and a means of restoration and rollback are in place before applying any such change in production.