draft
check cluster health
curl "http://elastic:9200/_cluster/health?pretty"
look for existing indices
curl "http://elastic:9200/_cat/indices?v"
curl -X DELETE "http://elastic:9200/INDEX-NAME"
https://www.elastic.co/guide/en/elastic-stack-overview/index.html old doc (6.3 - 7.4)
https://www.elastic.co/guide/en/elasticsearch/reference/index.html new doc