title: Read IOPS limits for RDS read-replica?
body: <p>I've noticed strange thing happened on my PostgreSQL Amazon RDS Read replica.</p>
  
  <p>We've done "stress-test" of dozens parallel high-load read requests. Performance was really good in the beginning of the test, but then rapidly decreased while PostgresSQL itself kept holding dozens of <code>select</code> queries which were performed fast before it stacked.</p>
  
  <p>I've opened Monitor statistics tab in RDS console and have seen that along with visible performance reducing Read IOPS number also decreased from 3000/sec to 300/sec and didn't go upper then 300/sec iops for long time.
  At the same time CPU usage was really low ~3%, there weren't any problems with RAM or storage space.</p>
  
  <p>So my question: are any documented limitations of Read IOPS for read replica? It looks like Amazon RDS automatically reduced high limit of IOPS after really high load (3000/sec).</p>
  
  <p><a href="https://i.stack.imgur.com/qqpPA.png" rel="nofollow"><img src="https://i.stack.imgur.com/qqpPA.png" alt="enter image description here"></a></p>
  
  <p>Read-replica server runs on db.t2.large instance with 100 GB General Purpose (SSD) storage type with disabled fixed IOPS feature.</p>