<style>
body {
    height: 2000px;
}

div {
  width: 300px;
  height: 300px;
  background-color: green;
}

.container {
  opacity: 0.9;
}

.absolute {
  position: absolute;
  left: 200px;
  top: 100px;
  background-color: blue;
  will-change: transform;
}
</style>

<div class=container><div class=fixed></div><div class=absolute></div></div>