JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">

<div class="box">
<div class="overlay">
Overlay

</div>
</div>

</div>
<div syle="height:1000px">

Test
</div>

CSS

.box{
  height:300px;
  width:3000px;
  background:white;
  border:1px solid black;
}
.overlay{
  position:fixed;
  left:50%;
  padding:10px;
  width:200px;
}
html,body{
  height:1000px;
}
.container{
    overflow-x: scroll;

}