Call me maybe: Elasticsearch by Kyle Kingsbury.
Kyle attempts to answer the question: How safe is data in Elasticsearch?.
I say “attempts,” Kyle does a remarkable job of documenting unanswered questions and conditions that can lead to data loss with Elasticsearch. But you will find there is no final answer to the safety question, despite deep analysis and research.
Klye is an Elasticsearch user and does provide some guidance on making your Elasticsearch installation safer, not safe but safer.
Must reading for all serious users of Elasticsearch.
I first saw this in a tweet by Andrew Purtell.