Changing log level and properties from HAC is often used by developers for various support things. Unfortunately on SAP Commerce Cloud (CCv2) there is no more such possibility, as HAC is not available on storefront nodes.
I had a task to optimize user creation and storing. Before changes on each anonymous checkout a new user was creates with ID in format RANDOM_UID|USER_EMAILand we had a lot of users who used anonymous checkout more than once. After changes only one user with ID in format USER_EMAIL for all anonymous checkouts was used. As a part of the task I need to migrate all old users to new format users. First version of moigration script had an execution time took more than 3 days for processing around 7 millions of people.