<!DOCTYPE html>

<html>
<head>
    <style>
        body {
            margin: 0;
        }
        .container {
            position: relative;
            z-index: 0;
            margin: 50px;
            width: 400px;
            height: 320px;
            overflow-y: scroll;
            border: 30px solid gray;
            box-shadow: 0 0 10px transparent;
            padding: 20px;
        }

        .inner {
            position: relative;
            height: 1000px;
            width: 100%;
            background-color: silver;
        }
        
        .inner-fixed {
            position: absolute;
            top: 50px;
            left: 100px;
            width: 200px;
            height: 150px;
            background-color: green;
            box-shadow: 0 0 10px transparent;
            will-change: transform;
        }
        
        .placeholder {
            position: absolute;
            background-color: red;
            top: 50px;
            left: 100px;
            width: 200px;
            height: 148px;
        }

        .scrollbar-hider {
            position: absolute;
            height: 380px;
            width: 37px;
            top: 70px;
            left: 484px;
            background-color: black;
        }
    </style>
</head>
<body>

<div id="scroller" class="container">
    <div class="inner">
        &nbsp;
        <div class="placeholder"></div>
        <div class="inner-fixed"></div>
    </div>
</div>
<div class="scrollbar-hider"></div>

</body>
</html>