title: How Create a Scheduler (e.g. to schedule tweets, or an api request)
body: <p>I have a table of schedule items, they may be scheduled for the same time. I'm wondering how to have them all execute at the correct time when:</p>
  
  <p>The problem I see is that executing one scheduled item (like a scheduled twitter post) requires an API request which may take up to a second or two - probably longer. If I execute them sequentially + there are too many scheduled items at the same time, the time they get executed at could be after the scheduled time.</p>
  
  <p>How would I go about building this "scheduling" system that avoids these problems? Any tips, advice?</p>
  
  <p>Thanks!</p>