JSFiddle - React, Tailwind, and code Playground

HTML

<div class="first">
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />abc<br />
    abc<br />abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    abc<br />
    <div class="second">
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />xyz<br />
        xyz<br />xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
        xyz<br />
    </div>
</div>

CSS

.first {width:300px; height:300px; border:1px solid #000; overflow:auto; position:fixed; text-align:center}
.second {width:100px; height:100%; position:absolute; top:0; right:0; border:1px solid blue; text-align:center; overflow:auto}