diff --git a/docs/upgrade-guide.md b/docs/upgrade-guide.md
index b26e3985f4d..d23dd2e987b 100644
--- a/docs/upgrade-guide.md
+++ b/docs/upgrade-guide.md
@@ -57,6 +57,12 @@ For any custom needs, these parameters can be overwritten by updating them in [`
 
 The `assembleShaders` function was moved to luma.gl in v4.1 and is no longer re-exported from deck.gl. As described in v4.1 upgrade guide please use `Model` class instead or import it from luma.gl.
 
+
+### Removed Immutable support
+
+`ScatterplotLayer` and `PolygonLayer` supported immutable/ES6 containers using [`get`](https://github.com/uber/deck.gl/blob/master/src/core/utils/get.js) method, due to performance reasons this support has been dropped.
+
+
 ## Upgrading from deck.gl v4 to v4.1
 
 deck.gl v4.1 is a backward-compatible release. Most of the functionality and APIs remain unchanged but there are smaller changes that might requires developers' attention if they **develop custom layers**. Note that applications that are only using the provided layers should not need to make any changes issues.
diff --git a/docs/whats-new.md b/docs/whats-new.md
index a86181bb149..26bad038061 100644
--- a/docs/whats-new.md
+++ b/docs/whats-new.md
@@ -6,14 +6,6 @@ All new additions to the official deck.gl 5.0 API are listed here. Note that in
 
 As always, for information on deprecations and how to update your code in response to any API changes, please read the deck.gl [Upgrade Guide](/docs/get-started/upgrade-guide.md).
 
-## DeckGL: Performance Boost
-
-Immutable support is dropped.
-
-Layer initialization, rendering and picking performance are improved.
-
-> TODO - Add more description
-
 ## DeckGL: Control over DevicePixelRatio
 
 The new `useDevicePixels` prop on the `DeckGL` React component can be used to disable usage of full resolution on retina/HD displays. Disabling deck.gl's default behavior of always rendering at maximum device resolution can reduce the render buffer size with a factor of 4x on retina devices and lead to significant performance improvements on typical fragment shader bound rendering. This option can be especially interesting on "retina" type mobile phone displays where pixels are so small that the visual quality loss may be largely imperceptible.