What normally works
Normally our search is powered by a super powerful search engine, to allow you to Search All The Things.
What works during the maintenance window
When we are performing DB maintenance on the search engine we fall back to a simpler database query, so basically, the individual pages, Customers, Tickets, Inventory, etc. has basic search capabilities.
Search All The Things is limited while the search database is undergoing maintenance.
Hope this helps to explain what is going on during maintenance!