Algolia is best known for its search-as-a-service product. It lets you integrate real-time search in your app or website using a developer-friendly API.

They are the default search app choice for a number of the headless platforms out there. I think they still have quite a ways to run, and could end up being scooped up by one of the larger platforms.

TechCrunch: Search API startup Algolia raises $150 million at $2.25 billion valuation