@Hari hmm. Yes, that’s been an issue for years. The real problem with Flarum is that despite what they’ll tell you, the calls to the database are what slows it down, and the more extensions you have, the worse this gets. Any search facility should be core - it shouldn’t have to be added as a plugin or extension, and the fact that it’s taken Flarum so long to address what I’d consider a show stopper (a bit like their lack of interest around the GDPR subject) in my view.
mongoDB is so much faster as it’s not tied into SQL and is based on collections of data. And who uses MyISAM in mySQL these days ? InnoDB is indeed much faster, but it cannot compete with the speed of mongoDB.
Finally, another huge drawback is Flarum’s usage of PHP. This is notoriously slow in some cases, and when aligned with NodeJS, there is no contest in terms of speed. Search something in this forum and watch how quickly it returns data.