add a comment about the specialized GET requests path

Author: gaelgatelement

charts/matrix-stack/configs/synapse/path_map_file_get.tpl

@@ -9,7 +9,22 @@ SPDX-License-Identifier: AGPL-3.0-only
 # A map file that is used in haproxy config to map from matrix paths to the
 # named backend. The format is: path_regexp backend_name
 {{ if dig "client-reader" "enabled" false $root.Values.synapse.workers }}
-^/_matrix/client/(api/v1|r0|v3|unstable)/pushrules/ client-reader
+{{- /*
+The client-reader worker could also support the following GET requests
+when the related workers are not enabled. To keep things simple, we don't support
+this optimization here and we invite the chart user to directly deploy the related
+workers instead if these requests path are under high load.
+
+# push-rules
+^/\_matrix/client/(api/v1|r0|v3|unstable)/pushrules/
+
+# receipts-account
+^/\_matrix/client/(r0|v3|unstable)/._/tags
+^/\_matrix/client/(r0|v3|unstable)/._/account\_data
+
+# presence
+^/\_matrix/client/(api/v1|r0|v3|unstable)/presence/
+*/}}
 ^/_matrix/client/unstable/org.matrix.msc4140/delayed_events client-reader
 ^/_matrix/client/(api/v1|r0|v3|unstable)/devices/ client-reader
 {{- end }}