Fix Multistore FF for empty DB - another way

config/initializers/active_record_transaction_observer.rb

 # frozen_string_literal: true
 
-return unless Gitlab.com? || Gitlab.dev_or_test_env?
-
 def feature_flags_available?
   # When the DBMS is not available, an exception (e.g. PG::ConnectionBad) is raised
   active_db_connection = ActiveRecord::Base.connection.active? rescue false
@@ -11,6 +9,8 @@ rescue ActiveRecord::NoDatabaseError
   false
 end
 
+return unless Gitlab.com? || Gitlab.dev_or_test_env?
+
 Gitlab::Application.configure do
   if feature_flags_available? && ::Feature.enabled?(:active_record_transactions_tracking, type: :ops, default_enabled: :yaml)
     Gitlab::Database::Transaction::Observer.register!

lib/gitlab/redis/multi_store.rb

@@ -95,11 +95,15 @@ module Gitlab
       end
 
       def use_primary_and_secondary_stores?
-        Feature.enabled?("use_primary_and_secondary_stores_for_#{instance_name.underscore}", default_enabled: :yaml) && !same_redis_store?
+        feature_flags_available? &&
+          Feature.enabled?("use_primary_and_secondary_stores_for_#{instance_name.underscore}", default_enabled: :yaml) &&
+          !same_redis_store?
       end
 
       def use_primary_store_as_default?
-        Feature.enabled?("use_primary_store_as_default_for_#{instance_name.underscore}", default_enabled: :yaml) && !same_redis_store?
+        feature_flags_available? &&
+          Feature.enabled?("use_primary_store_as_default_for_#{instance_name.underscore}", default_enabled: :yaml) &&
+          !same_redis_store?
       end
 
       private