But I think the recommendations the post are entirely reasonable:
My recommendations for Elasticsearch users are unchanged: store your data in a database with better safety guarantees, and continuously upsert every document from that database into Elasticsearch. If your search engine is missing a few documents for a day, it’s not a big deal; they’ll be reinserted on the next run and appear in subsequent searches. Not using Elasticsearch as a system of record also insulates you from having to worry about ES downtime during elections.
Sphinx has some curious features, like being able to run as a MySQL storage engine (no doubt the result of the author being ex-MySQL), but it's also got most of the features that you come to expect in search engine, so I think it's fair to call it a competitor. That said, we still use ES.
We also built https://techusearch.com which uses Sphinx indexes (think of a SaaS version of Elasticsearch backed by Sphinx).
DISCLAIMER: I work for Basho.
Just remember the golden rule of architecture. Always assume every component will catastrophically fail at some point and design accordingly. In the case of ElasticSearch/Solr it means don't use it as a primary data store, backup regularly and have a mechanism to insert deltas.
https://developer.marklogic.com/learn/2009-07-search-api-wal...
They also have Alert queries, which are similar to ElasticSearch percolation feature.
MarkLogic is also an ACID compliant store with configurable HA, as well as asynch replication to a remote site. it could potentially serve if correctly configured, as the primary store.
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ArangoDB might have these capabilities as well. And again, it is an ACID compliant database so the data committed, the indices, and the resulting searches should respect transactional boundaries at any moment of time. I had not looked at ArangoDB deep enough to understand what limitations it might have though. It does not have similarity search capability, and hierarchical data like ElasticSearch has https://docs.arangodb.com/2.3/IndexHandling/Fulltext.html ----
I checked RethinkDB, and it appears that it suggests to integrate with ElasticSearch, meaning that elastic search will have a copy of the data from Rethink (and therefore subject to commit protocol of ElasticSearch)
--- Somebody already mentioned Riak with search capability. I think this one is much more similar to Marklogic's capability (and it is free) The advantage of these types of systems is that your primary store and text indexes are sitting on top of the single copy of data (or replicated invisibly within the infrastructure) http://docs.basho.com/riak/latest/dev/using/search/
Another Lucene base tech is RavenDb but IIRC it's for microsoft.
what else offer something like ES? Any lucene based nosql, ES is lucened base anyway. You can roll your own and use Lucene library.