The production build actually runs rather smoothly and it has a steady framerate of abt 40-50fps even when panning the map. When it first ingest the bulk of entities, it took about at least less than a second to render.
But the dev server would take more than that to render and it kind of freezes the webpage till it finished rendering. Plus it was rather lag after rendered, especially when panning the map.
Fyi, i previously used pre-built cesium and it actually did not exhibit the symptoms mentioned. But back then Cesim 1.34 unminified build was used.
The reason why i changed to cesium source later due to fact that the later cesium versions (eg 1.38) cannot be import using prebuilt due to error:missing third party pako library.
Thanks and regards