They are one of the very few companies in that space which still develop their own search technology instead of just adopting and mixing available open source packages. Most other search software these days runs on some flavour of Lucene and rightfully so IMO because Lucene is a rock solid piece of software.

This means that creating a defensible USP in that space isn't easy. Algolia did it by essentially developing their own search software from the ground up. It isn't necessarily better than competitors like Elasticsearch in every measure but it certainly has some interesting properties and it can be pretty fast, especially for things like autocomplete.