I'm very concerned about this too.
Making the functionality of the Program or modified version available to third parties as a service includes, without limitation, enabling third parties to interact with the functionality of the Program or modified version remotely through a computer network, offering a service the value of which entirely or primarily derives from the value of the Program or modified version, or offering a service that accomplishes for users the primary purpose of the Program or modified version.
"Interacting with the functionality of the program" is a very broad description, and sounds like if an end user does anything that touches an elasticsearch API then it's triggered.
The FAQ clarifies this:
I'm a user, how does this affect me?
If you download and use our default distribution of Elasticsearch and Kibana, nothing changes for you. Our default distribution continues to be free and open under the Elastic License, as it has been for nearly the last three years. If you build applications on top of Elasticsearch, nothing changes for you. Our client libraries continue to be licensed under Apache 2.0. If you use plugins on top of Elasticsearch or Kibana, nothing changes for you.
But my understanding is that one agrees to a license, not to a license+faq combination.
I love Elasticsearch and believe that you have good intent here, just looking to protect yourselves from AWS launching a separate Elasticsearch service. If the FAQ is meant to modify the license by excluding that condition then please consider using a different license that doesn't make us depend on your good will.