JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div id="content">
        <div class="test"></div>
    </div>
    <div class="overflow"></div>
</body>

CSS

html, body {
    margin:0;
    padding: 0;
}
#content {
    background: lime;
    overflow: auto;
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}

.overflow {
    position: fixed;
    right: 0;
    top: 0;
    bottom: 0;
    width: 10px;
    background: blue;
}

.test {
    background: red;
    height: 1000px;
    margin: 20px;
}