Elasticsearch 的主體是 Apache License 2.0，但 Elastic Stack (以前叫做 X-Pack) 則是需要付費使用的功能，其中包括了不少跟安全有關的項目在裡面，所以其實有不少人抱怨過產品凌駕安全性的問題，像是「ES 6.3: X-Pack Licence is "Expired" on New Install」這篇官方回應的：

A basic license is not entitled to security features. To try out security you need to use a trial license or obtain a subscription.

AWS 這次則是出手實作了他們自己的版本，叫做 Open Distro for Elasticsearch：「New – Open Distro for Elasticsearch」。

如果你看文章說明，他列出來的 feature 全部都是在 Elastic Stack 這頁上列出來的項目，針對性的意思其實很清楚了：

In addition to Elasticsearch and Kibana, the first release includes a set of advanced security, event monitoring & alerting, performance analysis, and SQL query features (more on those in a bit).

而前面提到的安全性功能也包括在內：

Security – This plugin that supports node-to-node encryption, five types of authentication (basic, Active Directory, LDAP, Kerberos, and SAML), role-based access controls at multiple levels (clusters, indices, documents, and fields), audit logging, and cross-cluster search so that any node in a cluster can run search requests across other nodes in the cluster.

目前支援 Docker Image 與 RPM，之後看看有沒有機會出 deb 版本：

In addition to the source code repo, Open Distro for Elasticsearch and Kibana are available as RPM and Docker containers, with separate downloads for the SQL JDBC and the PerfTop CLI.

這樣應該會讓 Elasticsearch 的服務模式受到很大的影響，來看 Elastic N.V. Ordinary Shares Real Time Stock Quotes 這邊會掉多少...