Opened project 'Bilder' containing 66,621 objects and tried search with both 'Index album objects' and 'Index metadata' enabled. Search form opens without delay and search is instantaneous.
My experience is similar, though with a couple of projects that are more in the 5000 objects range, not 50,000.
But my comments are things like "Ryan and Caroline at Cape Cod, May, 2019." For a similar image, MarkusD
would have a comment that included the entire geological history of Cape Cod (did you know that it's a gigantic terminal moraine, a remnant of the last ice age?), tide tables for Truro, a webcam pointed at the Provincetown pier, Ryan's report cards from kindergarten through third grade, and a video of Caroline's latest fabulous dance recital.
why I suggested turning off the metadata indexing.