added note on api workers

Author: adwk67

docs/modules/airflow/pages/troubleshooting/index.adoc

@@ -25,3 +25,29 @@ webservers: # Also add to other roles!
 ----
 
 See e.g. https://github.com/minio/minio/issues/20845[this MinIO issue] for details.
+
+== Setting API Workers
+
+In Airflow the webserver (called the API Server in Airflow 3.x+) can use multiple workers.
+This is determined by the environment variable `+AIRFLOW__API__WORKERS+` and is set by default to `4` in Airflow 2.x and `1` in Airflow 3.x+.
+The reason for this difference is that Airflow uses a backend library to manage child processes and in 3.x+ this library can cause child processes to be killed if a hard-coded startup timeout is exceeded.
+For most cases a default of `1` should be sufficient, but if you run into performance issues and would like to add more workers, you can either change the environment variable using `envOverrides`:
+
+[source,yaml]
+----
+webservers:
+  envOverrides:
+    AIRFLOW__API__WORKERS: 2 # something other than the default of 1
+----
+
+or modulate multiple worker processes at the level of webserver, keeping the default of a single worker per webserver:
+
+[source,yaml]
+----
+webservers:
+  roleGroups:
+    default:
+      replicas: 2 # add a replica (with a single worker)
+----
+
+TIP: Our recommendation is to increase the webserver replicas, with each webserver running a single worker, as this removes the risk of running into timeouts or memory issues.