M24-Release-Notes.md

@@ -8,6 +8,12 @@ For detailed services that are included in this release, please refer [here](htt
 
 ## :exclamation: Important Note
 
+Indexer service's Elasticsearch Java client SDK was [upgraded](
+https://community.opengroup.org/osdu/platform/system/indexer-service/-/merge_requests/788)
+to 7.17.22 in M24. It is **highly recommended** to upgrade your Elasticsearch server to v7.17.22 or higher. Elasticsearch Java client is [forward compatible](
+https://www.elastic.co/guide/en/elasticsearch/client/java-api-client/current/introduction.html#_elasticsearch_server_compatibility_policy)
+, but does not promise any backward compatibility. Indexer or Search service users may see Elasticsearch incompatibility issues if Elasticsearch server version is below v7.17.22.
+
 ### Sandbox/Incubator
 
 Project status: :exclamation: Updating... Please stay tuned.