I am summarizing from our old post, it should answer your queries
The Static Assembler allows you to pre-assemble and cache the rules of an application. Such pre-assembly is optional, but improves the response time for interactive users after system startup, especially after new ruleset versions are imported into a system, many rules have changed, or user profiles have changed to allow new or different ruleset versions.
1.) Are all rules in the rule caches flushed each time the Static Assembler is run? By this what we are asking is if the Static Assembler always does a full rule cache population or sometimes does delta loads.
Yes, all rules are flushed from the rule caches and re-populated on each execution of the Static Assembler.
2.) Does the Static Assembler cache all eligible rules in the DB into the rule caches or only rules that have been imported since the last time it was executed?
It caches all eligible rules in the DB into the rule caches.
It should work in Pega 7.2.1 on Pega Cloud as well
Once it is completed you would see something like this