diff --git a/doc/09-object-types.md b/doc/09-object-types.md
index 89b6ce102..17583f871 100644
--- a/doc/09-object-types.md
+++ b/doc/09-object-types.md
@@ -1229,6 +1229,11 @@ Configuration Attributes:
 Note: If `flush_threshold` is set too low, this will force the feature to flush all data to Elasticsearch too often.
 Experiment with the setting, if you are processing more than 1024 metrics per second or similar.
 
+> **Note**
+>
+> Be aware that `enable_send_perfdata` will create a new field mapping in the index for each performance data metric in a check plugin.
+> Elasticsearch/OpenSearch have a maximum number of fields in an index. The default value is usually 1000 fields. See [mapping settings limit](https://www.elastic.co/guide/en/elasticsearch/reference/8.18/mapping-settings-limit.html)
+
 Basic auth is supported with the `username` and `password` attributes. This requires an
 HTTP proxy (Nginx, etc.) in front of the Elasticsearch instance. Check [this blogpost](https://blog.netways.de/2017/09/14/secure-elasticsearch-and-kibana-with-an-nginx-http-proxy/)
 for an example.
@@ -1680,11 +1685,11 @@ Configuration Attributes:
   flush\_threshold          | Number                | **Optional.** How many data points to buffer before forcing a transfer to InfluxDB.  Defaults to `1024`.
   enable\_ha                | Boolean               | **Optional.** Enable the high availability functionality. Only valid in a [cluster setup](06-distributed-monitoring.md#distributed-monitoring-high-availability-features). Defaults to `false`.
 
-Note: If `flush_threshold` is set too low, this will always force the feature to flush all data
-to InfluxDB. Experiment with the setting, if you are processing more than 1024 metrics per second
-or similar.
-
-
+> **Note**
+>
+> If `flush_threshold` is set too low, this will always force the feature to flush all data
+> to InfluxDB. Experiment with the setting, if you are processing more than 1024 metrics per second
+> or similar.
 
 ### Influxdb2Writer <a id="objecttype-influxdb2writer"></a>
 
diff --git a/doc/14-features.md b/doc/14-features.md
index 843aa20f4..31697b27e 100644
--- a/doc/14-features.md
+++ b/doc/14-features.md
@@ -364,7 +364,8 @@ The following event types are written to Elasticsearch:
 * icinga2.event.notification
 
 Performance data metrics must be explicitly enabled with the `enable_send_perfdata`
-attribute.
+attribute. Be aware that this will create a new field mapping in the index for each performance data metric in a check plugin.
+See: [ElasticsearchWriter](09-object-types.md#objecttype-elasticsearchwriter)
 
 Metric values are stored like this: