JSFiddle - React, Tailwind, and code Playground

HTML

<div class="inflow">
    <div class="positioner"><!-- may not be needed: see notes below-->
      <div class="fixed"></div>
    </div>
  </div>

CSS

div.inflow {
  width: 200px; 
  height: 1000px; 
  border: 1px solid blue; 
  float: right; 
  position: relative; 
  margin-right: 100px;
}
div.positioner {position: absolute; right: 0;} /*may not be needed: see below*/
div.fixed {
  width: 80px; 
  border: 1px solid red; 
  height: 100px; 
  position: fixed; 
  top: 60px; 
  margin-left: 15px;
}