Creating subLayers using CARTO JS v4.1.8

Question

I created a simple map with multiple layers using the below code.

this.cartoSource = new carto.source.SQL(sql);
this.layerStyle  = new carto.style.CartoCSS(layerStyle);
this.layer = new carto.layer.Layer(this.cartoSource, this.layerStyle , layerOption);

Whenever there is a change in the source or firing feature_cover event, all map layers are repainted (a kind of flickering). why does a layer affect another independent layer?

My requirements are I have a layer with polygon shape. Whenever a user hovers over a particular polygon, that feature should be highlighted without repainting or flickering.

I tried two different ways:

1. I was updating layer style using setContent with the following code:

    #layer[cartodb_id=123]
            { 
                line-opacity: 1; 
                line-color: #FFF; 
                line-width: 1; 
                polygon-fill: #f4c650; 
            }

2. I was using another layer with one sql source with where condition where cartodb_id = FEATURE_OVER.data.cartodb_id.

Both are getting a flickering effect. How can I solve this issue?