Elasticsearch

Elasticsearch is a distributed RESTful search engine built for the cloud. Features include:

• Distributed and Highly Available Search Engine.
  • Each index is fully sharded with a configurable number of shards.
  • Each shard can have one or more replicas.
  • Read / Search operations performed on either one of the replica shard.
• Multi Tenant with Multi Types.
  • Support for more than one index.
  • Support for more than one type per index.
  • Index level configuration (number of shards, index storage, ...).
• Various set of APIs
  • HTTP RESTful API
  • Native Java API.
  • All APIs perform automatic node operation rerouting.
• Document oriented
  • No need for upfront schema definition.
  • Schema can be defined per type for customization of the indexing process.
• Reliable, Asynchronous Write Behind for long term persistency.
• (Near) Real Time Search.
• Built on top of Lucene
  • Each shard is a fully functional Lucene index
  • All the power of Lucene easily exposed through simple configuration / plugins.
• Per operation consistency
  • Single document level operations are atomic, consistent, isolated and durable.
• Open Source under the Apache License, version 2 ("ALv2")

This site uses Elastic Search for it's search functionality under the hood.