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Here search request is handled by Solr. Solr distributes queries to Solr agents and its aggregator is utilized. SolrCloud solves some issues related to index distribution. These issues are not relevant If the index is managed in Cache. So the Solr *Distributed Search* seems like a promising solution.

Before SolrCloud, Solr supported Distributed Search, which allowed one query to be executed across multiple shards, so the query was executed against the entire Solr index and no documents would be missed from the search results. So splitting the core across shards is not exclusively a SolrCloud concept. There were, however, several problems with the distributed approach that necessitated improvement with SolrCloud:

1. Splitting of the core into shards was somewhat manual.
2. There was no support for distributed indexing, which meant that you needed to explicitly send documents to a specific shard; Solr couldn't figure out on its own what shards to send documents to.
3. There was no load balancing or failover, so if you got a high number of queries, you needed to figure out where to send them and if one shard died it was just gone.

() User -> [Cache] : Search
node cluster {
 database {
 () indexPR1
 }

 [Cache] ..> [PR 1]
 [PR 1] --> [SolrServer]
 [SolrServer] --> [SolrPR1]
 [SolrPR1] -down-> [FSDirectoryPR1]
 [FSDirectoryPR1] -> indexPR1
 
 database {
 () indexPR2
 }

 [SolrServer] --> [SolrPR2]
 [SolrPR2] -down-> [FSDirectoryPR2]
 [FSDirectoryPR2] -> indexPR2
}

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