JSFiddle - React, Tailwind, and code Playground

HTML

<div class="sidebar">
    <div class="sidebar-inner">
        side bar content
    </div>
</div>
<div class="content"> 
    content
</div>

CSS

body {
    position: relative;
    margin: 0;
}
.sidebar {
    position: absolute;
    top: 0;
    bottom: 0;
    width: 100px;
    background: blue;
    left: 0;
}
.sidebar-inner {
   position: fixed;
    left: 0;
}
.content {
   width: 1400px;
    background: pink;
    height: 2000px;
}