How to speed up the Docsvision platform?

Question

Document flow

Good afternoon!
The essence of the problem: there is a workflow, on the Docsvision platform, with an iDoc client application and with a ms sql
database. The size of the database is 400GB
. e)
Archiving of cards was carried out from 2013 to 2016, but this did not speed up the work, maintenance plans (updating statistics, rebuilding, reorganizing indexes) in ms sql are configured and are being implemented.
How can you speed up the workflow?