diff --git a/gradle.properties b/gradle.properties
index afc97624..3b2fef5c 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -11,7 +11,7 @@ android.suppressUnsupportedOptionWarnings=android.suppressUnsupportedOptionWarni
 kotlin.code.style=official
 kotlin.mpp.stability.nowarn=true
 GROUP=dev.yorkie
-VERSION_NAME=0.4.21-rc
+VERSION_NAME=0.4.23
 POM_DESCRIPTION=Document store for building collaborative editing applications.
 POM_INCEPTION_YEAR=2022
 POM_URL=https://github.com/yorkie-team/yorkie-android-sdk
diff --git a/yorkie/src/androidTest/kotlin/dev/yorkie/document/json/JsonTreeTest.kt b/yorkie/src/androidTest/kotlin/dev/yorkie/document/json/JsonTreeTest.kt
index 32cd62e1..5f6f3487 100644
--- a/yorkie/src/androidTest/kotlin/dev/yorkie/document/json/JsonTreeTest.kt
+++ b/yorkie/src/androidTest/kotlin/dev/yorkie/document/json/JsonTreeTest.kt
@@ -3,6 +3,8 @@ package dev.yorkie.document.json
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import com.google.gson.reflect.TypeToken
 import dev.yorkie.TreeTest
+import dev.yorkie.api.toByteString
+import dev.yorkie.api.toCrdtTree
 import dev.yorkie.core.Client
 import dev.yorkie.core.Client.SyncMode.Manual
 import dev.yorkie.core.GENERAL_TIMEOUT
@@ -12,6 +14,7 @@ import dev.yorkie.core.withTwoClientsAndDocuments
 import dev.yorkie.document.Document
 import dev.yorkie.document.Document.Event.LocalChange
 import dev.yorkie.document.Document.Event.RemoteChange
+import dev.yorkie.document.crdt.toXml
 import dev.yorkie.document.json.JsonTree.ElementNode
 import dev.yorkie.document.json.JsonTree.TreeNode
 import dev.yorkie.document.json.TreeBuilder.element
@@ -2300,6 +2303,97 @@ class JsonTreeTest {
         }
     }
 
+    @Test
+    fun test_calculating_index_tree_size_during_concurrent_editing() {
+        withTwoClientsAndDocuments(syncMode = Manual) { c1, c2, d1, d2, _ ->
+            updateAndSync(
+                Updater(c1, d1) { root, _ ->
+                    root.setNewTree(
+                        "t",
+                        element("doc") {
+                            element("p") {
+                                text { "hello" }
+                            }
+                        },
+                    )
+                },
+                Updater(c2, d2),
+            )
+            assertTreesXmlEquals("<doc><p>hello</p></doc>", d1, d2)
+
+            updateAndSync(
+                Updater(c1, d1) { root, _ ->
+                    root.rootTree().edit(0, 7)
+                },
+                Updater(c2, d2) { root, _ ->
+                    root.rootTree().edit(1, 2, text { "p" })
+                },
+            ) {
+                assertTreesXmlEquals("<doc></doc>", d1)
+                assertEquals(0, d1.getRoot().rootTree().size)
+
+                assertTreesXmlEquals("<doc><p>pello</p></doc>", d2)
+                assertEquals(7, d2.getRoot().rootTree().size)
+            }
+
+            assertTreesXmlEquals("<doc></doc>", d1, d2)
+            assertEquals(d1.getRoot().rootTree().size, d2.getRoot().rootTree().size)
+        }
+    }
+
+    @Test
+    fun test_index_tree_consistency_from_snapshot() {
+        withTwoClientsAndDocuments(syncMode = Manual) { c1, c2, d1, d2, _ ->
+            updateAndSync(
+                Updater(c1, d1) { root, _ ->
+                    root.setNewTree(
+                        "t",
+                        element("r") {
+                            element("p")
+                        },
+                    )
+                },
+                Updater(c2, d2),
+            )
+            assertTreesXmlEquals("<r><p></p></r>", d1, d2)
+
+            updateAndSync(
+                Updater(c1, d1) { root, _ ->
+                    root.rootTree().edit(0, 2)
+                },
+                Updater(c2, d2) { root, _ ->
+                    root.rootTree().edit(1, 1, element("i") { text { "a" } })
+                    root.rootTree().edit(2, 3, text { "b" })
+                },
+            ) {
+                assertTreesXmlEquals("<r></r>", d1)
+                assertEquals(0, d1.getRoot().rootTree().size)
+
+                assertTreesXmlEquals("<r><p><i>b</i></p></r>", d2)
+                assertEquals(5, d2.getRoot().rootTree().size)
+            }
+            assertTreesXmlEquals("<r></r>", d1, d2)
+
+            val d1Nodes = mutableListOf<Triple<String, Int, Boolean>>()
+            val d2Nodes = mutableListOf<Triple<String, Int, Boolean>>()
+            val sNodes = mutableListOf<Triple<String, Int, Boolean>>()
+
+            d1.getRoot().rootTree().indexTree.traverseAll { node, _ ->
+                d1Nodes.add(Triple(node.toXml(), node.size, node.isRemoved))
+            }
+            d2.getRoot().rootTree().indexTree.traverseAll { node, _ ->
+                d2Nodes.add(Triple(node.toXml(), node.size, node.isRemoved))
+            }
+            val sRoot = d1.getRoot().target["t"].toByteString().toCrdtTree()
+            sRoot.indexTree.traverseAll { node, _ ->
+                sNodes.add(Triple(node.toXml(), node.size, node.isRemoved))
+            }
+
+            assertEquals(d1Nodes, d2Nodes)
+            assertEquals(d1Nodes, sNodes)
+        }
+    }
+
     companion object {
 
         fun JsonObject.rootTree() = getAs<JsonTree>("t")
diff --git a/yorkie/src/main/kotlin/dev/yorkie/document/crdt/CrdtTree.kt b/yorkie/src/main/kotlin/dev/yorkie/document/crdt/CrdtTree.kt
index cab39a70..2b9d5401 100644
--- a/yorkie/src/main/kotlin/dev/yorkie/document/crdt/CrdtTree.kt
+++ b/yorkie/src/main/kotlin/dev/yorkie/document/crdt/CrdtTree.kt
@@ -862,11 +862,7 @@ internal data class CrdtTreeNode private constructor(
             removedAt = executedAt
         }
         if (alived) {
-            if (parent?.removedAt == null) {
-                updateAncestorSize()
-            } else {
-                requireNotNull(parent).size -= paddedSize
-            }
+            updateAncestorSize()
         }
     }
 
diff --git a/yorkie/src/main/kotlin/dev/yorkie/util/IndexTree.kt b/yorkie/src/main/kotlin/dev/yorkie/util/IndexTree.kt
index 95b509d8..9d846aff 100644
--- a/yorkie/src/main/kotlin/dev/yorkie/util/IndexTree.kt
+++ b/yorkie/src/main/kotlin/dev/yorkie/util/IndexTree.kt
@@ -444,6 +444,9 @@ internal abstract class IndexTreeNode<T : IndexTreeNode<T>> {
 
         while (parent != null) {
             parent.size += paddedSize * sign
+            if (parent.isRemoved) {
+                break
+            }
             parent = parent.parent
         }
     }
@@ -453,12 +456,9 @@ internal abstract class IndexTreeNode<T : IndexTreeNode<T>> {
      * the tree is newly created and the size of the descendants is not calculated.
      */
     fun updateDescendantSize(): Int {
-        if (isRemoved) {
-            size = 0
-            return 0
+        size += children.sumOf { node ->
+            node.updateDescendantSize().takeUnless { node.isRemoved } ?: 0
         }
-
-        size += children.sumOf { it.updateDescendantSize() }
         return paddedSize
     }