diff --git a/docs/api/world.md b/docs/api/world.md
index c75217e..c04b8c1 100755
--- a/docs/api/world.md
+++ b/docs/api/world.md
@@ -603,12 +603,26 @@ function World:exists(
 
 ## cleanup
 
-Cleans up deleted entities and their associated data. This is automatically called by jecs, but can be called manually if needed.
+Cleans up empty archetypes.
 
 ```luau
 function World:cleanup(): void
 ```
 
+:::info
+It is recommended to profile the optimal interval you should cleanup because it varies completely from game to game.
+
+Here are a couple of reasons from Sander Mertens:
+	- some applications are memory constrained, so any wasted memory on empty
+	  archetypes has to get cleaned up
+	- many archetypes can get created during game startup but aren't used later
+	  on, so it would be wasteful to keep them around
+	- empty archetypes can slow queries down, especially if there are many more
+	  empty ones than non-empty ones
+	- if the total number of component permutations (/relationships) is too
+	  high, you have no choice but to periodically cleanup empty archetypes
+:::
+
 Example:
 
 ::: code-group
diff --git a/jecs.luau b/jecs.luau
index c6880f6..0fea236 100755
--- a/jecs.luau
+++ b/jecs.luau
@@ -74,7 +74,7 @@ type query = {
 	filter_with: { i53 },
 	filter_without: { i53 },
 	next: () -> (i53, ...any),
-	world: World,
+	world: world,
 }
 
 export type observer = {
@@ -1181,9 +1181,10 @@ local function query_archetypes(query: query)
 		compatible_archetypes = {}
 		query.compatible_archetypes = compatible_archetypes
 
-		local archetypes = query.world.archetypes
+		local world = query.world
+		local archetypes = world.archetypes
 
-		local component_index = query.world.component_index
+		local component_index = world.component_index
 
 		local idr: componentrecord?
 		local with = query.filter_with
diff --git a/package.json b/package.json
index b4805ac..611edcd 100755
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "@rbxts/jecs",
-	"version": "0.9.0-rc.11",
+	"version": "0.9.0-rc.12",
 	"description": "Stupidly fast Entity Component System",
 	"main": "jecs.luau",
 	"repository": {
diff --git a/wally.toml b/wally.toml
index 8ae400a..2a5ff37 100755
--- a/wally.toml
+++ b/wally.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ukendio/jecs"
-version = "0.9.0-rc.11"
+version = "0.9.0-rc.12"
 registry = "https://github.com/UpliftGames/wally-index"
 realm = "shared"
 license = "MIT"