SyncDbAfterInactivity shows the minimum time after db was changed to call db.Sync regular Db.Sync will help to decrease the chance of data loss in case of power loss/bsod while this logic decrease the chance some db writer will need to wait for sync to finish.

SyncDbAfterVersions is the fallback mechanism in case there are some active write is happening so SyncDbAfterInactivity mechanism is not triggered usually change in the object produces 1 max in the localstore/spacestore db experimentally we found that 1 min of active writing produces about 150 versions in each of localstore and spacestore dbs so we set this value of 500 will make sure that in case of non-stop writing we will sync db at least once per 3 min.