group member count optimization

app/models/group_account.rb

@@ -21,10 +21,20 @@ class GroupAccount < ApplicationRecord
   validates :account_id, uniqueness: { scope: :group_id }
 
   after_commit :remove_relationship_cache
+  after_create :increment_member_count
+  after_destroy :decrement_member_count
 
   private
 
   def remove_relationship_cache
     Rails.cache.delete("relationship:#{account_id}:group#{group_id}")
   end
+
+  def increment_member_count
+    group&.increment!(:member_count)
+  end
+
+  def decrement_member_count
+    group&.decrement!(:member_count)
+  end
 end