diff --git a/prod-upgrade/mongo/mongo.yaml b/prod-upgrade/mongo/mongo.yaml
index 85534ad..0bccda3 100644
--- a/prod-upgrade/mongo/mongo.yaml
+++ b/prod-upgrade/mongo/mongo.yaml
@@ -66,10 +66,6 @@ spec:
               mountPath: /data/db
             - name: mongo-conf
               mountPath: /etc/mongodb
-            - name: mongo-keyfile
-              mountPath: /etc/keyfile.0
-              subPath: keyfile.0
-              readOnly: true
       volumes:
       - name: mongo-data
         hostPath:
@@ -98,6 +94,7 @@ spec:
           value: "mongo"
           effect: "NoSchedule"
 
+# function: when primary node changes, update mongo-rs0 to primary;
 ---
 apiVersion: v1
 kind: Service