In the SLM 9.0.0 Core changes doc there is a section that reads:
2.3 SNOW LICENSE MANAGER INVENTORY SERVICE
In Snow License Manager 9 and Snow Inventory 6, an API has been introduced to allow the deletion of computers, devices, and users asynchronously outside of the Data Update Job, thus increasing performance and robustness. To authenticate, Snow License Manager gathers the API URIs and authentication keys that are set up and stored in each configured SnowInventory database connection. These use port 80 by default; however, they can be configured in Snow Inventory to use HTTPS. By default, the Snow License Manager Inventory service runs every sixth hour and sends delete requests to any Snow Inventory APIs that are configured. These deletions in the SnowInventory database are handled by the Snow Inventory server garbage collection.
This is followed up by a really good KB article explaining the new process here.
However, in my experience, I have Deleted computers from an environment with an instantaneous effect within the SLM view. Since moving to SLM 9, the computers can still be seen in SLM after I delete them. The section and KB talk about a change in the process of removing the computers from Inventory ultimately. Should the experience within SLM still be instantaneous? This is not discussed in the KB.