diff --git a/action_get_user_id.go b/action_get_user_id.go
index 42930bc..20086f9 100644
--- a/action_get_user_id.go
+++ b/action_get_user_id.go
@@ -18,6 +18,10 @@ func (s Service) GetUserIDByAuthToken(authToken string) (userID string) {
 		}
 	)
 
+	if authToken == "" {
+		return
+	}
+
 	// Find
 	if err := col.FindOne(ctx, cond).Decode(&device); err != nil {
 		logger.Error("devicemngmt - getUserIDByAuthToken", logger.LogData{
@@ -30,3 +34,31 @@ func (s Service) GetUserIDByAuthToken(authToken string) (userID string) {
 	userID = device.UserID.Hex()
 	return
 }
+
+// GetUserIDByDeviceId ...
+func (s Service) GetUserIDByDeviceId(deviceId string) (userID string) {
+	var (
+		ctx    = context.Background()
+		col    = s.getDeviceCollection()
+		device = Device{}
+		cond   = bson.M{
+			"deviceId": deviceId,
+		}
+	)
+
+	if deviceId == "" {
+		return
+	}
+
+	// Find
+	if err := col.FindOne(ctx, cond).Decode(&device); err != nil {
+		logger.Error("devicemngmt - getUserIDByDeviceId", logger.LogData{
+			"deviceId": deviceId,
+			"err":      err.Error(),
+		})
+		return
+	}
+
+	userID = device.UserID.Hex()
+	return
+}