Algolia delivers web search products via a SaaS (software as a service) model.
Although in-site search has long been available from general search providers such as Google, this is usually done as a subset of general web search. The search engine then crawls the web as a whole and the client site, then offers search functions that are limited to that site. Algolia's product only indexes the websites of their customers, making the search much easier and faster.
A lot of optimization has also been made because the search model is intended to provide better performance and user experience. Algolia can be compared to an in-house search engine that works on the native website backend database, but with the simplicity of using a site-restricted Google search.
Want to know more: https://www.algolia.com/