I see. So in this example, it definitely is requiring each tag individually. I imagine the performance impact is the use of IN and then doing it 3 times (one for each tag).
I also wonder if the search can be smarter about this? Only use IN when multiple tags are provided, otherwise use =
If you alter your search to tags:wa,gastroenterology,female does it work better? Granted, it changes the query, as it won’t be topics that have all three, but topics that have any of the three.
Right now tags does not have a performant way to do AND and that is being requested at
ping @alehandrof, you might find this interesting