Do you need something beyond "highly scalable search solution"? A lot of enterprises (and I'd guess startups too!) need good search solutions and your two players in the Java space (that I know of) are Solr and Elasticsearch. We are using Solr in our product, but the more I hear about Elasticsearch the more I want to give it a serious try.
My reason for not using it originally was that we had prototyped our solution using Compass (which was the project before Elasticsearch) only to have it abandoned to work on Elasticsearch. So I was concerned about the "one dev" model and losing something that was a key component of what we needed.
Since then I've not been impressed with SolrCloud (would love to hear good experiences, but it seems their distributed model isn't right) and have been giving Elasticsearch serious thought again.
"In the Java space" meaning deployed in a Java servlet container. Both are stand-alone search servers, exposing their API for search and indexing through HTTP using XML and/or JSON.
> "In the Java space" meaning deployed in a Java servlet container.
I didn't say nor mean to imply that. Technically, Solr is based on servlet technology whether stand-alone or not, you can choose to deploy it in a web container of your choice or use the Jetty instance it comes with for the "stand-alone" experience. I don't know much about Elasticsearch's architecture personally.
My reason for not using it originally was that we had prototyped our solution using Compass (which was the project before Elasticsearch) only to have it abandoned to work on Elasticsearch. So I was concerned about the "one dev" model and losing something that was a key component of what we needed.
Since then I've not been impressed with SolrCloud (would love to hear good experiences, but it seems their distributed model isn't right) and have been giving Elasticsearch serious thought again.