I was going to use FeatureLayer with client-side graphics ("source" property) but faced with a significant rendering delay during layer initialization. Here is an example: https://codepen.io/parshin/pen/gObVZvZ?editors=1000
This example is based on Custom WebGL layer view code sample with two additions:
The Custom WebGL layer is rendered almost immediately after pressing the button. The FeatureLayer (white labels) appears on the map only after several seconds.
Why does that delay happen? Is there any way to eliminate/reduce it?