Solr indexing involves huge costs. Therefore, handling of real-time data is expensive. Every time a new piece of information comes into the system, it has to be indexed to be available for search. Another way of handling this is to break the Solr index into two parts, stable and unstable. The stable part of the index is contained inside Solr, while the unstable part can be handled by a plugin by extracting information from Redis. The unstable part of the index, which is now inside Redis, can handle real-time additions and deletions through an external script, which is reflected in the search results.

Redis is an advanced key value store that can be used to store documents containing keys and values in the memory. It offers advantages over Memcache, as it syncs the data onto disk and provides replication and clustering facilities. In addition to the storage of normal key values, it provides facilities to store data structures such as strings, hashes, lists, sets, and...