add index

db/migrate/20250617075609_add_submissions_template_index.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddSubmissionsTemplateIndex < ActiveRecord::Migration[8.0]
+  def change
+    add_index :submissions, %i[account_id template_id id], where: 'archived_at IS NULL'
+  end
+end