Elasticsearch, the heart of the stack
Elasticsearch is the core of the entire stack. It is a search platform built on the Lucene library and developed in Java.
Elasticsearch was officially released in 2010 by the creator, Shay Bannon, who had created another search engine that was the precursor to Elasticsearch, called Compass.
Elasticsearch hosts a common JSON over HTTP interface that allows Elasticsearch to act as the search tier for an application frontend or directly via an Application Programming Interface (API):
{
  "name" : "packtpub.lan",
  "cluster_name" : "cluster",
  "cluster_uuid" : "GcrS1m99QIWPjkgT9SKnuA",
  "version" : {
    "number" : "7.10.2",
    "build_flavor" : "default",
    "build_type" : "tar",
   ...