More efficient query for watched_by? and use etag for the status

app/controllers/cards/watches_controller.rb

@@ -1,6 +1,10 @@
 class Cards::WatchesController < ApplicationController
   include CardScoped
 
+  def show
+    fresh_when etag: @card.watch_for(Current.user)
+  end
+
   def create
     @card.watch_by Current.user
   end

app/models/card/watchable.rb

@@ -9,7 +9,11 @@ module Card::Watchable
   end
 
   def watched_by?(user)
-    watchers.include?(user)
+    watch_for(user)&.watching?
+  end
+
+  def watch_for(user)
+    watches.find_by(user: user)
   end
 
   def watch_by(user)