According to T168061#5386265, we should see similar (actually better) search behavior by switching to Phabricator's built in search engine. It's not the same as what we used previously, the built in search has been overhauled completely since the last time we used it.
As I said in that other task, I think we should do a trial run with the built in search engine and see if people notice an improvement (or regression). Importantly, we should also track any effects on database server load.
After a short trial, if everything seems to be performing well, then we can consider disabling elasticsearch once again.