The clear cache API allows to clear either all caches or specific cached associated with one ore more indices.
$ curl -XPOST 'http://localhost:9200/twitter/_cache/clear'
The API, by default, will clear all cached. Specific caches can cleaned explicitly by setting filter, field_data or bloom to true.
The flush API can be applied to more than one index with a single call, or even on _all the indices.
$ curl -XPOST 'http://localhost:9200/kimchy,elasticsearch/_cache/clear'
$ curl -XPOST 'http://localhost:9200/_cache/clear'