diff --git a/src/document/crdt/root.ts b/src/document/crdt/root.ts
index 9b67a56bc..beecb02f3 100644
--- a/src/document/crdt/root.ts
+++ b/src/document/crdt/root.ts
@@ -171,26 +171,22 @@ export class CRDTRoot {
   public deregisterElement(element: CRDTElement): number {
     let count = 0;
 
-    const callback = (elem: CRDTElement) => {
+    const deregisterElementInternal = (elem: CRDTElement) => {
       const createdAt = elem.getCreatedAt().toIDString();
       this.elementPairMapByCreatedAt.delete(createdAt);
       this.removedElementSetByCreatedAt.delete(createdAt);
       count++;
-    };
-    const deregisterDescendants = (container: CRDTContainer) => {
-      container.getDescendants((elem) => {
-        callback(elem);
-        if (elem instanceof CRDTContainer) {
-          deregisterDescendants(elem);
-        }
-        return false;
-      });
+
+      if (elem instanceof CRDTContainer) {
+        elem.getDescendants((e) => {
+          deregisterElementInternal(e);
+          return false;
+        });
+      }
     };
 
-    callback(element);
-    if (element instanceof CRDTContainer) {
-      deregisterDescendants(element);
-    }
+    deregisterElementInternal(element);
+
     return count;
   }
 
diff --git a/src/document/json/array.ts b/src/document/json/array.ts
index ca26f17f4..7c58d347e 100644
--- a/src/document/json/array.ts
+++ b/src/document/json/array.ts
@@ -326,19 +326,19 @@ export class ArrayProxy {
   }
 
   /**
-   * `buildArray` constructs an array of CRDTElements based on the user-provided array.
+   * `buildArrayElements` constructs array elements based on the user-provided array.
    */
-  public static buildArray(
+  public static buildArrayElements(
     context: ChangeContext,
     value: Array<unknown>,
   ): Array<CRDTElement> {
-    const elementArray: Array<CRDTElement> = [];
+    const elements: Array<CRDTElement> = [];
     for (const v of value) {
       const createdAt = context.issueTimeTicket();
       const elem = buildCRDTElement(context, v, createdAt);
-      elementArray.push(elem);
+      elements.push(elem);
     }
-    return elementArray;
+    return elements;
   }
 
   /**
diff --git a/src/document/json/element.ts b/src/document/json/element.ts
index 3c28bb71a..65e679414 100644
--- a/src/document/json/element.ts
+++ b/src/document/json/element.ts
@@ -150,7 +150,7 @@ export function buildCRDTElement(
   } else if (Array.isArray(value)) {
     element = CRDTArray.create(
       createdAt,
-      ArrayProxy.buildArray(context, value),
+      ArrayProxy.buildArrayElements(context, value),
     );
   } else if (typeof value === 'object') {
     if (value instanceof Text) {
@@ -169,7 +169,7 @@ export function buildCRDTElement(
     } else {
       element = CRDTObject.create(
         createdAt,
-        ObjectProxy.buildObject(context, value!),
+        ObjectProxy.buildObjectMembers(context, value!),
       );
     }
   } else {
diff --git a/src/document/json/object.ts b/src/document/json/object.ts
index 030d6b488..e594d13da 100644
--- a/src/document/json/object.ts
+++ b/src/document/json/object.ts
@@ -163,16 +163,16 @@ export class ObjectProxy {
   }
 
   /**
-   * `buildObject` constructs an object where all values from the
+   * `buildObjectMembers` constructs an object where all values from the
    * user-provided object are transformed into CRDTElements.
    * This function takes an object and iterates through its values,
    * converting each value into a corresponding CRDTElement.
    */
-  public static buildObject(
+  public static buildObjectMembers(
     context: ChangeContext,
     value: object,
   ): { [key: string]: CRDTElement } {
-    const elementObject: { [key: string]: CRDTElement } = {};
+    const members: { [key: string]: CRDTElement } = {};
     for (const [k, v] of Object.entries(value)) {
       if (k.includes('.')) {
         throw new YorkieError(
@@ -183,9 +183,9 @@ export class ObjectProxy {
 
       const createdAt = context.issueTimeTicket();
       const elem = buildCRDTElement(context, v, createdAt);
-      elementObject[k] = elem;
+      members[k] = elem;
     }
-    return elementObject;
+    return members;
   }
 
   /**
diff --git a/src/document/operation/remove_operation.ts b/src/document/operation/remove_operation.ts
index 666d24f5f..5e88da410 100644
--- a/src/document/operation/remove_operation.ts
+++ b/src/document/operation/remove_operation.ts
@@ -23,7 +23,10 @@ import {
   OperationInfo,
   ExecutionResult,
 } from '@yorkie-js-sdk/src/document/operation/operation';
-import { CRDTContainer } from '@yorkie-js-sdk/src/document/crdt/element';
+import {
+  CRDTContainer,
+  CRDTElement,
+} from '@yorkie-js-sdk/src/document/crdt/element';
 import { CRDTObject } from '@yorkie-js-sdk/src/document/crdt/object';
 import { CRDTArray } from '@yorkie-js-sdk/src/document/crdt/array';
 import { SetOperation } from '@yorkie-js-sdk/src/document/operation/set_operation';
@@ -61,23 +64,19 @@ export class RemoveOperation extends Operation {
     root: CRDTRoot,
     source: OpSource,
   ): ExecutionResult | undefined {
-    const parentObject = root.findByCreatedAt(
+    const container = root.findByCreatedAt(
       this.getParentCreatedAt(),
     ) as CRDTContainer;
-    if (!parentObject) {
+    if (!container) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
     }
-    if (!(parentObject instanceof CRDTContainer)) {
-      logger.fatal(`only object and array can execute remove: ${parentObject}`);
+    if (!(container instanceof CRDTContainer)) {
+      logger.fatal(`only object and array can execute remove: ${container}`);
     }
 
     // NOTE(chacha912): Handle cases where operation cannot be executed during undo and redo.
     if (source === OpSource.UndoRedo) {
-      const targetElem = parentObject.getByID(this.createdAt);
-      if (targetElem?.isRemoved()) {
-        return;
-      }
-      let parent: CRDTContainer | undefined = parentObject;
+      let parent: CRDTElement | undefined = container.getByID(this.createdAt);
       while (parent) {
         if (parent.getRemovedAt()) {
           return;
@@ -85,14 +84,14 @@ export class RemoveOperation extends Operation {
         parent = root.findElementPairByCreatedAt(parent.getCreatedAt())?.parent;
       }
     }
-    const key = parentObject.subPathOf(this.createdAt);
-    const reverseOp = this.toReverseOperation(parentObject);
+    const key = container.subPathOf(this.createdAt);
+    const reverseOp = this.toReverseOperation(container);
 
-    const elem = parentObject.delete(this.createdAt, this.getExecutedAt());
+    const elem = container.delete(this.createdAt, this.getExecutedAt());
     root.registerRemovedElement(elem);
 
     const opInfos: Array<OperationInfo> =
-      parentObject instanceof CRDTArray
+      container instanceof CRDTArray
         ? [
             {
               type: 'remove',
diff --git a/src/document/operation/set_operation.ts b/src/document/operation/set_operation.ts
index 0d8d7240d..5d68dd8c8 100644
--- a/src/document/operation/set_operation.ts
+++ b/src/document/operation/set_operation.ts
@@ -67,17 +67,17 @@ export class SetOperation extends Operation {
     root: CRDTRoot,
     source: OpSource,
   ): ExecutionResult | undefined {
-    const parentObject = root.findByCreatedAt(this.getParentCreatedAt());
-    if (!parentObject) {
+    const obj = root.findByCreatedAt(this.getParentCreatedAt()) as CRDTObject;
+    if (!obj) {
       logger.fatal(`fail to find ${this.getParentCreatedAt()}`);
     }
-    if (!(parentObject instanceof CRDTObject)) {
+    if (!(obj instanceof CRDTObject)) {
       logger.fatal(`fail to execute, only object can execute set`);
     }
-    const obj = parentObject as CRDTObject;
+
     // NOTE(chacha912): Handle cases where operation cannot be executed during undo and redo.
     if (source === OpSource.UndoRedo) {
-      let parent: CRDTContainer | undefined = obj;
+      let parent: CRDTElement | undefined = obj;
       while (parent) {
         if (parent.getRemovedAt()) {
           return;