Like Solr, ElasticSearch is a search engine service that’s built on top of Lucene. It’s a younger project, aimed more at people in the web world (in contrast to Solr’s heavy use in enterprises). It allows you to update the search index with much lower latency, has a more minimal REST/JSON-based interface and configuration options, and scales horizontally in a more seamless way. It doesn’t yet have the community or number of contributors of the more established project, though, and it is missing some of the broader features that Solr offers, so it’s worth evaluating both.
