title: Need a mix of Delayed and Map
body: <p>I have an application without a save button; saving happens automatically in the background. As the user works with the app, tasks are created and put into a queue for execution. Some of them are delayed, for example, when you start typing, I wait 200ms before I update the corresponding value in the database.</p>
  
  <p>To make this more simple to use code wise, I'd like to be able to add a task to the queue with a delay and a "key". If there is already a task with the same "key", then my second task should be ignored (because the same operation is already queued).</p>
  
  <p>Does something like that already exist?</p>