PERF: Throttle updates to API key last_used_at (#16390)

Co-authored-by: David Taylor <david@taylorhq.com>

app/models/api_key.rb

@@ -67,6 +67,13 @@ class ApiKey < ActiveRecord::Base
 
     api_key_scopes.blank? || api_key_scopes.any? { |s| s.permits?(env) }
   end
+
+  def update_last_used!(now = Time.zone.now)
+    return if last_used_at && (last_used_at > 1.minute.ago)
+
+    # using update_column to avoid the AR transaction
+    update_column(:last_used_at, now)
+  end
 end
 
 # == Schema Information

lib/auth/default_current_user_provider.rb

@@ -385,7 +385,9 @@ class Auth::DefaultCurrentUserProvider
         end
 
       if user && can_write?
-        api_key.update_columns(last_used_at: Time.zone.now)
+        Scheduler::Defer.later "Updating api_key last_used" do
+          api_key.update_last_used!
+        end
       end
 
       user