Algolia is a powerful search and analytics platform designed to help developers create powerful, engaging search experiences for their users. With Algolia, developers can speed up search results, optimize search relevance and improve user experience with advanced search features such as filtering, faceting and pagination. Algolia also helps developers customize their search results for different audiences and content types. Algolia also offers powerful analytics tools to help developers measure and understand how their users are interacting with their search results. With Algolia, developers can build smarter search experiences that help their users find the most relevant content quickly and easily.
More control over the search relevancy feature and the ability to customize results for individual search results. More tools for non-technical users, e.g., you can use your web crawler to ingest content into the search engine instead of submitting it via the API.
Good value for money and super easy to integrate.
elasticsearch
Apache Solr
Expertrec Search Engine
Sphinx (search engine)
swiftype
Site Search 360
Xapian
Manticore search
OpenSearchServer
Whoosh
Cludo Site Search
Measured Search
SearchTap.io
RediSearch
ItemsAPI
Heritrix
Google Custom Search Engine
SearchBlox
Vespa
fully hosted, support and help to improve search ranking.