diff --git a/.travis.yml b/.travis.yml
index 6a542fc7b..a143860b6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,7 +7,7 @@ language: node_js
 services:
 - xvfb
 node_js:
-- '8'
+- '10'
 cache:
   yarn: true
 branches:
diff --git a/src/model/documentfragment.js b/src/model/documentfragment.js
index 79926943e..2224237f6 100644
--- a/src/model/documentfragment.js
+++ b/src/model/documentfragment.js
@@ -133,7 +133,7 @@ export default class DocumentFragment {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'documentFragment' || type == 'model:documentFragment';
+		return type === 'documentFragment' || type === 'model:documentFragment';
 	}
 
 	/**
diff --git a/src/model/documentselection.js b/src/model/documentselection.js
index 214bfd48b..b97752846 100644
--- a/src/model/documentselection.js
+++ b/src/model/documentselection.js
@@ -382,7 +382,7 @@ export default class DocumentSelection {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'selection' ||
+		return type === 'selection' ||
 			type == 'model:selection' ||
 			type == 'documentSelection' ||
 			type == 'model:documentSelection';
diff --git a/src/model/element.js b/src/model/element.js
index 59c14e1c8..202771e8f 100644
--- a/src/model/element.js
+++ b/src/model/element.js
@@ -116,13 +116,14 @@ export default class Element extends Node {
 	 * @returns {Boolean}
 	 */
 	is( type, name = null ) {
-		const cutType = type.replace( /^model:/, '' );
-
 		if ( !name ) {
-			return cutType == 'element' || cutType == this.name || super.is( type );
-		} else {
-			return cutType == 'element' && name == this.name;
+			return type === 'element' || type === 'model:element' ||
+				type === this.name || type === 'model:' + this.name ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'node' || type === 'model:node';
 		}
+
+		return name === this.name && ( type === 'element' || type === 'model:element' );
 	}
 
 	/**
diff --git a/src/model/liveposition.js b/src/model/liveposition.js
index 8aaccbc68..a577d7b67 100644
--- a/src/model/liveposition.js
+++ b/src/model/liveposition.js
@@ -80,7 +80,9 @@ export default class LivePosition extends Position {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'livePosition' || type == 'model:livePosition' || super.is( type );
+		return type === 'livePosition' || type === 'model:livePosition' ||
+			// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+			type == 'position' || type === 'model:position';
 	}
 
 	/**
diff --git a/src/model/liverange.js b/src/model/liverange.js
index b11121cba..a6b6402d3 100644
--- a/src/model/liverange.js
+++ b/src/model/liverange.js
@@ -57,7 +57,9 @@ export default class LiveRange extends Range {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'liveRange' || type == 'model:liveRange' || super.is( type );
+		return type === 'liveRange' || type === 'model:liveRange' ||
+			// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+			type == 'range' || type === 'model:range';
 	}
 
 	/**
diff --git a/src/model/markercollection.js b/src/model/markercollection.js
index 4d9a5a7d6..33def0b15 100644
--- a/src/model/markercollection.js
+++ b/src/model/markercollection.js
@@ -463,7 +463,7 @@ class Marker {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'marker' || type == 'model:marker';
+		return type === 'marker' || type === 'model:marker';
 	}
 
 	/**
diff --git a/src/model/node.js b/src/model/node.js
index d85bb8055..42d5976d6 100644
--- a/src/model/node.js
+++ b/src/model/node.js
@@ -10,7 +10,6 @@
 import toMap from '@ckeditor/ckeditor5-utils/src/tomap';
 import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
 import compareArrays from '@ckeditor/ckeditor5-utils/src/comparearrays';
-
 // To check if component is loaded more than once.
 import '@ckeditor/ckeditor5-utils/src/version';
 
@@ -432,7 +431,7 @@ export default class Node {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'node' || type == 'model:node';
+		return type === 'node' || type === 'model:node';
 	}
 
 	/**
@@ -500,11 +499,3 @@ export default class Node {
 		this._attrs.clear();
 	}
 }
-
-/**
- * The node's parent does not contain this node.
- *
- * This error may be thrown from corrupted trees.
- *
- * @error model-node-not-found-in-parent
- */
diff --git a/src/model/position.js b/src/model/position.js
index 6bc5f2206..795d6d12e 100644
--- a/src/model/position.js
+++ b/src/model/position.js
@@ -10,8 +10,6 @@
 import TreeWalker from './treewalker';
 import compareArrays from '@ckeditor/ckeditor5-utils/src/comparearrays';
 import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
-import Text from './text';
-import { last } from 'lodash-es';
 
 // To check if component is loaded more than once.
 import '@ckeditor/ckeditor5-utils/src/version';
@@ -81,9 +79,13 @@ export default class Position {
 			);
 		}
 
-		// Normalize the root and path (if element was passed).
-		path = root.getPath().concat( path );
-		root = root.root;
+		// Normalize the root and path when element (not root) is passed.
+		if ( root.is( 'rootElement' ) ) {
+			path = path.slice();
+		} else {
+			path = [ ...root.getPath(), ...path ];
+			root = root.root;
+		}
 
 		/**
 		 * Root of the position path.
@@ -141,7 +143,7 @@ export default class Position {
 	 * @type {Number}
 	 */
 	get offset() {
-		return last( this.path );
+		return this.path[ this.path.length - 1 ];
 	}
 
 	/**
@@ -216,9 +218,7 @@ export default class Position {
 	 * @type {module:engine/model/text~Text|null}
 	 */
 	get textNode() {
-		const node = this.parent.getChild( this.index );
-
-		return ( node instanceof Text && node.startOffset < this.offset ) ? node : null;
+		return getTextNodeAtPosition( this, this.parent );
 	}
 
 	/**
@@ -228,17 +228,23 @@ export default class Position {
 	 * @type {module:engine/model/node~Node|null}
 	 */
 	get nodeAfter() {
-		return this.textNode === null ? this.parent.getChild( this.index ) : null;
+		// Cache the parent and reuse for performance reasons. See #6579 and #6582.
+		const parent = this.parent;
+
+		return getNodeAfterPosition( this, parent, getTextNodeAtPosition( this, parent ) );
 	}
 
 	/**
 	 * Node directly before this position or `null` if this position is in text node.
 	 *
 	 * @readonly
-	 * @type {Node}
+	 * @type {module:engine/model/node~Node|null}
 	 */
 	get nodeBefore() {
-		return this.textNode === null ? this.parent.getChild( this.index - 1 ) : null;
+		// Cache the parent and reuse for performance reasons. See #6579 and #6582.
+		const parent = this.parent;
+
+		return getNodeBeforePosition( this, parent, getTextNodeAtPosition( this, parent ) );
 	}
 
 	/**
@@ -339,10 +345,12 @@ export default class Position {
 	 * @returns {Array.<module:engine/model/item~Item>} Array with ancestors.
 	 */
 	getAncestors() {
-		if ( this.parent.is( 'documentFragment' ) ) {
-			return [ this.parent ];
+		const parent = this.parent;
+
+		if ( parent.is( 'documentFragment' ) ) {
+			return [ parent ];
 		} else {
-			return this.parent.getAncestors( { includeSelf: true } );
+			return parent.getAncestors( { includeSelf: true } );
 		}
 	}
 
@@ -540,7 +548,7 @@ export default class Position {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'position' || type == 'model:position';
+		return type === 'position' || type === 'model:position';
 	}
 
 	/**
@@ -840,7 +848,7 @@ export default class Position {
 
 		// Then, add the rest of the path.
 		// If this position is at the same level as `from` position nothing will get added.
-		combined.path = combined.path.concat( this.path.slice( i + 1 ) );
+		combined.path = [ ...combined.path, ...this.path.slice( i + 1 ) ];
 
 		return combined;
 	}
@@ -1057,3 +1065,91 @@ export default class Position {
  *
  * @typedef {String} module:engine/model/position~PositionStickiness
  */
+
+/**
+ * Returns a text node at the given position.
+ *
+ * This is a helper function optimized to reuse the position parent instance for performance reasons.
+ *
+ * Normally, you should use {@link module:engine/model/position~Position#textNode `Position#textNode`}.
+ * If you start hitting performance issues with {@link module:engine/model/position~Position#parent `Position#parent`}
+ * check if your algorithm does not access it multiple times (which can happen directly or indirectly via other position properties).
+ *
+ * See https://github.com/ckeditor/ckeditor5/issues/6579.
+ *
+ * See also:
+ *
+ * * {@link module:engine/model/position~getNodeAfterPosition}
+ * * {@link module:engine/model/position~getNodeBeforePosition}
+ *
+ * @param {module:engine/model/position~Position} position
+ * @param {module:engine/model/element~Element|module:engine/model/documentfragment~DocumentFragment} positionParent The parent of the
+ * given position.
+ * @returns {module:engine/model/text~Text|null}
+ */
+export function getTextNodeAtPosition( position, positionParent ) {
+	const node = positionParent.getChild( positionParent.offsetToIndex( position.offset ) );
+
+	if ( node && node.is( 'text' ) && node.startOffset < position.offset ) {
+		return node;
+	}
+
+	return null;
+}
+
+/**
+ * Returns the node after the given position.
+ *
+ * This is a helper function optimized to reuse the position parent instance and the calculation of the text node at the
+ * specific position for performance reasons.
+ *
+ * Normally, you should use {@link module:engine/model/position~Position#nodeAfter `Position#nodeAfter`}.
+ * If you start hitting performance issues with {@link module:engine/model/position~Position#parent `Position#parent`} and/or
+ * {@link module:engine/model/position~Position#textNode `Position#textNode`}
+ * check if your algorithm does not access those properties multiple times
+ * (which can happen directly or indirectly via other position properties).
+ *
+ * See https://github.com/ckeditor/ckeditor5/issues/6579 and https://github.com/ckeditor/ckeditor5/issues/6582.
+ *
+ * See also:
+ *
+ * * {@link module:engine/model/position~getTextNodeAtPosition}
+ * * {@link module:engine/model/position~getNodeBeforePosition}
+ *
+ * @param {module:engine/model/position~Position} position
+ * @param {module:engine/model/element~Element|module:engine/model/documentfragment~DocumentFragment} positionParent The parent of the
+ * given position.
+ * @param {module:engine/model/text~Text|null} textNode Text node at the given position.
+ * @returns {module:engine/model/node~Node|null}
+ */
+export function getNodeAfterPosition( position, positionParent, textNode ) {
+	if ( textNode !== null ) {
+		return null;
+	}
+
+	return positionParent.getChild( positionParent.offsetToIndex( position.offset ) );
+}
+
+/**
+ * Returns the node before the given position.
+ *
+ * Refer to {@link module:engine/model/position~getNodeBeforePosition} for documentation on when to use this util method.
+ *
+ * See also:
+ *
+ * * {@link module:engine/model/position~getTextNodeAtPosition}
+ * * {@link module:engine/model/position~getNodeAfterPosition}
+ *
+ * @param {module:engine/model/position~Position} position
+ * @param {module:engine/model/element~Element|module:engine/model/documentfragment~DocumentFragment} positionParent The parent of the
+ * given position.
+ * @param {module:engine/model/text~Text|null} textNode Text node at the given position.
+ * @returns {module:engine/model/node~Node|null}
+ */
+export function getNodeBeforePosition( position, positionParent, textNode ) {
+	if ( textNode !== null ) {
+		return null;
+	}
+
+	return positionParent.getChild( positionParent.offsetToIndex( position.offset ) - 1 );
+}
diff --git a/src/model/range.js b/src/model/range.js
index 559fb20cb..743f09bd7 100644
--- a/src/model/range.js
+++ b/src/model/range.js
@@ -158,7 +158,7 @@ export default class Range {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'range' || type == 'model:range';
+		return type === 'range' || type === 'model:range';
 	}
 
 	/**
diff --git a/src/model/rootelement.js b/src/model/rootelement.js
index 2d29cac2d..39e21239a 100644
--- a/src/model/rootelement.js
+++ b/src/model/rootelement.js
@@ -80,12 +80,19 @@ export default class RootElement extends Element {
 	 * @returns {Boolean}
 	 */
 	is( type, name ) {
-		const cutType = type.replace( 'model:', '' );
 		if ( !name ) {
-			return cutType == 'rootElement' || super.is( type );
-		} else {
-			return ( cutType == 'rootElement' && name == this.name ) || super.is( type, name );
+			return type === 'rootElement' || type === 'model:rootElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'element' || type === 'model:element' ||
+				type === this.name || type === 'model:' + this.name ||
+				type === 'node' || type === 'model:node';
 		}
+
+		return name === this.name && (
+			type === 'rootElement' || type === 'model:rootElement' ||
+			// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+			type === 'element' || type === 'model:element'
+		);
 	}
 
 	/**
@@ -105,3 +112,4 @@ export default class RootElement extends Element {
 	// @if CK_DEBUG_ENGINE // 	console.log( 'ModelRootElement: ' + this );
 	// @if CK_DEBUG_ENGINE // }
 }
+
diff --git a/src/model/selection.js b/src/model/selection.js
index 18e7ebef4..b1a38af56 100644
--- a/src/model/selection.js
+++ b/src/model/selection.js
@@ -632,7 +632,7 @@ export default class Selection {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'selection' || type == 'model:selection';
+		return type === 'selection' || type === 'model:selection';
 	}
 
 	/**
diff --git a/src/model/text.js b/src/model/text.js
index 56bcafd33..7e9c0edf6 100644
--- a/src/model/text.js
+++ b/src/model/text.js
@@ -82,7 +82,9 @@ export default class Text extends Node {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'text' || type == 'model:text' || super.is( type );
+		return type === 'text' || type === 'model:text' ||
+			// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+			type === 'node' || type === 'model:node';
 	}
 
 	/**
diff --git a/src/model/textproxy.js b/src/model/textproxy.js
index f3946f8c4..91610f364 100644
--- a/src/model/textproxy.js
+++ b/src/model/textproxy.js
@@ -178,7 +178,7 @@ export default class TextProxy {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'textProxy' || type == 'model:textProxy';
+		return type === 'textProxy' || type === 'model:textProxy';
 	}
 
 	/**
diff --git a/src/model/treewalker.js b/src/model/treewalker.js
index f70da7700..bcf0b5288 100644
--- a/src/model/treewalker.js
+++ b/src/model/treewalker.js
@@ -10,7 +10,12 @@
 import Text from './text';
 import TextProxy from './textproxy';
 import Element from './element';
-import Position from './position';
+import {
+	default as Position,
+	getTextNodeAtPosition,
+	getNodeAfterPosition,
+	getNodeBeforePosition
+} from './position';
 import CKEditorError from '@ckeditor/ckeditor5-utils/src/ckeditorerror';
 
 /**
@@ -225,7 +230,11 @@ export default class TreeWalker {
 			return { done: true };
 		}
 
-		const node = position.textNode ? position.textNode : position.nodeAfter;
+		// Get node just after the current position.
+		// Use a highly optimized version instead of checking the text node first and then getting the node after. See #6582.
+		const positionParent = position.parent;
+		const textNodeAtPosition = getTextNodeAtPosition( position, positionParent );
+		const node = textNodeAtPosition ? textNodeAtPosition : getNodeAfterPosition( position, positionParent, textNodeAtPosition );
 
 		if ( node instanceof Element ) {
 			if ( !this.shallow ) {
@@ -299,8 +308,11 @@ export default class TreeWalker {
 			return { done: true };
 		}
 
-		// Get node just before current position
-		const node = position.textNode ? position.textNode : position.nodeBefore;
+		// Get node just before the current position.
+		// Use a highly optimized version instead of checking the text node first and then getting the node before. See #6582.
+		const positionParent = position.parent;
+		const textNodeAtPosition = getTextNodeAtPosition( position, positionParent );
+		const node = textNodeAtPosition ? textNodeAtPosition : getNodeBeforePosition( position, positionParent, textNodeAtPosition );
 
 		if ( node instanceof Element ) {
 			position.offset--;
diff --git a/src/model/writer.js b/src/model/writer.js
index d5b26cee6..9b3cf5357 100644
--- a/src/model/writer.js
+++ b/src/model/writer.js
@@ -1360,14 +1360,14 @@ export default class Writer {
 			const markerRange = marker.getRange();
 			let isAffected = false;
 
-			if ( type == 'move' ) {
+			if ( type === 'move' ) {
 				isAffected =
 					positionOrRange.containsPosition( markerRange.start ) ||
 					positionOrRange.start.isEqual( markerRange.start ) ||
 					positionOrRange.containsPosition( markerRange.end ) ||
 					positionOrRange.end.isEqual( markerRange.end );
 			} else {
-				// if type == 'merge'.
+				// if type === 'merge'.
 				const elementBefore = positionOrRange.nodeBefore;
 				const elementAfter = positionOrRange.nodeAfter;
 
diff --git a/src/view/attributeelement.js b/src/view/attributeelement.js
index 626e470d1..2e7a46fb4 100644
--- a/src/view/attributeelement.js
+++ b/src/view/attributeelement.js
@@ -157,12 +157,18 @@ export default class AttributeElement extends Element {
 	 * @returns {Boolean}
 	 */
 	is( type, name = null ) {
-		const cutType = type && type.replace( /^view:/, '' );
-
 		if ( !name ) {
-			return cutType == 'attributeElement' || super.is( type );
+			return type === 'attributeElement' || type === 'view:attributeElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === this.name || type === 'view:' + this.name ||
+				type === 'element' || type === 'view:element' ||
+				type === 'node' || type === 'view:node';
 		} else {
-			return ( cutType == 'attributeElement' && name == this.name ) || super.is( type, name );
+			return name === this.name && (
+				type === 'attributeElement' || type === 'view:attributeElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'element' || type === 'view:element'
+			);
 		}
 	}
 
diff --git a/src/view/containerelement.js b/src/view/containerelement.js
index 753b71867..a4ae85727 100644
--- a/src/view/containerelement.js
+++ b/src/view/containerelement.js
@@ -83,11 +83,18 @@ export default class ContainerElement extends Element {
 	 * @returns {Boolean}
 	 */
 	is( type, name = null ) {
-		const cutType = type && type.replace( /^view:/, '' );
 		if ( !name ) {
-			return cutType == 'containerElement' || super.is( type );
+			return type === 'containerElement' || type === 'view:containerElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === this.name || type === 'view:' + this.name ||
+				type === 'element' || type === 'view:element' ||
+				type === 'node' || type === 'view:node';
 		} else {
-			return ( cutType == 'containerElement' && name == this.name ) || super.is( type, name );
+			return name === this.name && (
+				type === 'containerElement' || type === 'view:containerElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'element' || type === 'view:element'
+			);
 		}
 	}
 }
diff --git a/src/view/documentfragment.js b/src/view/documentfragment.js
index 1bda12313..7e42a1af5 100644
--- a/src/view/documentfragment.js
+++ b/src/view/documentfragment.js
@@ -118,7 +118,7 @@ export default class DocumentFragment {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'documentFragment' || type == 'view:documentFragment';
+		return type === 'documentFragment' || type === 'view:documentFragment';
 	}
 
 	/**
diff --git a/src/view/documentselection.js b/src/view/documentselection.js
index 0e6d5d644..2b9341737 100644
--- a/src/view/documentselection.js
+++ b/src/view/documentselection.js
@@ -292,7 +292,7 @@ export default class DocumentSelection {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'selection' ||
+		return type === 'selection' ||
 			type == 'documentSelection' ||
 			type == 'view:selection' ||
 			type == 'view:documentSelection';
diff --git a/src/view/editableelement.js b/src/view/editableelement.js
index b6ca91c6f..293b69b34 100644
--- a/src/view/editableelement.js
+++ b/src/view/editableelement.js
@@ -95,11 +95,20 @@ export default class EditableElement extends ContainerElement {
 	 * @returns {Boolean}
 	 */
 	is( type, name = null ) {
-		const cutType = type && type.replace( /^view:/, '' );
 		if ( !name ) {
-			return cutType == 'editableElement' || super.is( type );
+			return type === 'editableElement' || type === 'view:editableElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'containerElement' || type === 'view:containerElement' ||
+				type === this.name || type === 'view:' + this.name ||
+				type === 'element' || type === 'view:element' ||
+				type === 'node' || type === 'view:node';
 		} else {
-			return ( cutType == 'editableElement' && name == this.name ) || super.is( type, name );
+			return name === this.name && (
+				type === 'editableElement' || type === 'view:editableElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'containerElement' || type === 'view:containerElement' ||
+				type === 'element' || type === 'view:element'
+			);
 		}
 	}
 
diff --git a/src/view/element.js b/src/view/element.js
index 9bd3efebb..ae5f93b9b 100644
--- a/src/view/element.js
+++ b/src/view/element.js
@@ -176,11 +176,13 @@ export default class Element extends Node {
 	 * @returns {Boolean}
 	 */
 	is( type, name = null ) {
-		const cutType = type.replace( /^view:/, '' );
 		if ( !name ) {
-			return cutType == 'element' || cutType == this.name || super.is( type );
+			return type === this.name || type === 'view:' + this.name ||
+				type === 'element' || type === 'view:element' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'node' || type === 'view:node';
 		} else {
-			return cutType == 'element' && name == this.name;
+			return name === this.name && ( type === 'element' || type === 'view:element' );
 		}
 	}
 
diff --git a/src/view/emptyelement.js b/src/view/emptyelement.js
index 39182de91..76b8c0b3d 100644
--- a/src/view/emptyelement.js
+++ b/src/view/emptyelement.js
@@ -74,11 +74,17 @@ export default class EmptyElement extends Element {
 	 * @returns {Boolean}
 	 */
 	is( type, name = null ) {
-		const cutType = type.replace( /^view:/, '' );
 		if ( !name ) {
-			return cutType == 'emptyElement' || super.is( type );
+			return type === 'emptyElement' || type === 'view:emptyElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === this.name || type === 'view:' + this.name ||
+				type === 'element' || type === 'view:element' ||
+				type === 'node' || type === 'view:node';
 		} else {
-			return ( cutType == 'emptyElement' && name == this.name ) || super.is( type, name );
+			return name === this.name && (
+				type === 'emptyElement' || type === 'view:emptyElement' ||
+				type === 'element' || type === 'view:element'
+			);
 		}
 	}
 
diff --git a/src/view/node.js b/src/view/node.js
index 719120930..6347b00e0 100644
--- a/src/view/node.js
+++ b/src/view/node.js
@@ -339,7 +339,7 @@ export default class Node {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'node' || type == 'view:node';
+		return type === 'node' || type === 'view:node';
 	}
 
 	/**
diff --git a/src/view/position.js b/src/view/position.js
index 782673309..b925b201d 100644
--- a/src/view/position.js
+++ b/src/view/position.js
@@ -222,7 +222,7 @@ export default class Position {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'position' || type == 'view:position';
+		return type === 'position' || type === 'view:position';
 	}
 
 	/**
diff --git a/src/view/range.js b/src/view/range.js
index d140a6ac6..6286cee2b 100644
--- a/src/view/range.js
+++ b/src/view/range.js
@@ -449,7 +449,7 @@ export default class Range {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'range' || type == 'view:range';
+		return type === 'range' || type === 'view:range';
 	}
 
 	/**
diff --git a/src/view/rooteditableelement.js b/src/view/rooteditableelement.js
index 75337cb21..577bab8d8 100644
--- a/src/view/rooteditableelement.js
+++ b/src/view/rooteditableelement.js
@@ -68,11 +68,22 @@ export default class RootEditableElement extends EditableElement {
 	 * @returns {Boolean}
 	 */
 	is( type, name = null ) {
-		const cutType = type.replace( /^view:/, '' );
 		if ( !name ) {
-			return cutType == 'rootElement' || super.is( type );
+			return type === 'rootElement' || type === 'view:rootElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'editableElement' || type === 'view:editableElement' ||
+				type === 'containerElement' || type === 'view:containerElement' ||
+				type === this.name || type === 'view:' + this.name ||
+				type === 'element' || type === 'view:element' ||
+				type === 'node' || type === 'view:node';
 		} else {
-			return ( cutType == 'rootElement' && name == this.name ) || super.is( type, name );
+			return name === this.name && (
+				type === 'rootElement' || type === 'view:rootElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === 'editableElement' || type === 'view:editableElement' ||
+				type === 'containerElement' || type === 'view:containerElement' ||
+				type === 'element' || type === 'view:element'
+			);
 		}
 	}
 
diff --git a/src/view/selection.js b/src/view/selection.js
index f9d213d62..d00c82ab3 100644
--- a/src/view/selection.js
+++ b/src/view/selection.js
@@ -590,7 +590,7 @@ export default class Selection {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'selection' || type == 'view:selection';
+		return type === 'selection' || type === 'view:selection';
 	}
 
 	/**
diff --git a/src/view/text.js b/src/view/text.js
index 27636d59f..3e6ef0190 100644
--- a/src/view/text.js
+++ b/src/view/text.js
@@ -60,7 +60,9 @@ export default class Text extends Node {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'text' || type == 'view:text' || super.is( type );
+		return type === 'text' || type === 'view:text' ||
+			// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+			type === 'node' || type === 'view:node';
 	}
 
 	/**
diff --git a/src/view/textproxy.js b/src/view/textproxy.js
index ab829088e..cc98f3803 100644
--- a/src/view/textproxy.js
+++ b/src/view/textproxy.js
@@ -156,7 +156,7 @@ export default class TextProxy {
 	 * @returns {Boolean}
 	 */
 	is( type ) {
-		return type == 'textProxy' || type == 'view:textProxy';
+		return type === 'textProxy' || type === 'view:textProxy';
 	}
 
 	/**
diff --git a/src/view/uielement.js b/src/view/uielement.js
index c2f2a0718..3e39586d4 100644
--- a/src/view/uielement.js
+++ b/src/view/uielement.js
@@ -87,11 +87,17 @@ export default class UIElement extends Element {
 	 * @returns {Boolean}
 	 */
 	is( type, name = null ) {
-		const cutType = type.replace( /^view:/, '' );
 		if ( !name ) {
-			return cutType == 'uiElement' || super.is( type );
+			return type === 'uiElement' || type === 'view:uiElement' ||
+				// From super.is(). This is highly utilised method and cannot call super. See ckeditor/ckeditor5#6529.
+				type === this.name || type === 'view:' + this.name ||
+				type === 'element' || type === 'view:element' ||
+				type === 'node' || type === 'view:node';
 		} else {
-			return ( cutType == 'uiElement' && name == this.name ) || super.is( type, name );
+			return name === this.name && (
+				type === 'uiElement' || type === 'view:uiElement' ||
+				type === 'element' || type === 'view:element'
+			);
 		}
 	}
 
diff --git a/tests/model/position.js b/tests/model/position.js
index 043221db5..2c6d3b6e6 100644
--- a/tests/model/position.js
+++ b/tests/model/position.js
@@ -8,7 +8,12 @@ import DocumentFragment from '../../src/model/documentfragment';
 import Element from '../../src/model/element';
 import Text from '../../src/model/text';
 import TextProxy from '../../src/model/textproxy';
-import Position from '../../src/model/position';
+import {
+	default as Position,
+	getTextNodeAtPosition,
+	getNodeAfterPosition,
+	getNodeBeforePosition
+} from '../../src/model/position';
 import Range from '../../src/model/range';
 import MarkerOperation from '../../src/model/operation/markeroperation';
 import AttributeOperation from '../../src/model/operation/attributeoperation';
@@ -485,10 +490,12 @@ describe( 'Position', () => {
 		} );
 	} );
 
-	it( 'should have proper parent path', () => {
-		const position = new Position( root, [ 1, 2, 3 ] );
+	describe( 'getParentPath()', () => {
+		it( 'should have proper parent path', () => {
+			const position = new Position( root, [ 1, 2, 3 ] );
 
-		expect( position.getParentPath() ).to.deep.equal( [ 1, 2 ] );
+			expect( position.getParentPath() ).to.deep.equal( [ 1, 2 ] );
+		} );
 	} );
 
 	describe( 'isBefore()', () => {
@@ -1275,4 +1282,39 @@ describe( 'Position', () => {
 			expect( positionB.getCommonAncestor( positionA ) ).to.equal( lca );
 		}
 	} );
+
+	describe( 'getTextNodeAtPosition() util', () => {
+		it( 'returns a text node at the given position', () => {
+			const position = new Position( root, [ 1, 0, 1 ] );
+			const positionParent = position.parent;
+
+			expect( getTextNodeAtPosition( position, positionParent ) ).to.equal( foz );
+		} );
+
+		// This util is covered with tests by Position#textNode tests.
+	} );
+
+	describe( 'getNodeAfterPosition() util', () => {
+		it( 'returns a node after the position', () => {
+			const position = new Position( root, [ 1, 0 ] );
+			const positionParent = position.parent;
+			const textNode = getTextNodeAtPosition( position, positionParent );
+
+			expect( getNodeAfterPosition( position, positionParent, textNode ) ).to.equal( li1 );
+		} );
+
+		// This util is covered with tests by Position#nodeAfter tests.
+	} );
+
+	describe( 'getNodeBeforePosition() util', () => {
+		it( 'returns a node before the position', () => {
+			const position = new Position( root, [ 1, 1 ] );
+			const positionParent = position.parent;
+			const textNode = getTextNodeAtPosition( position, positionParent );
+
+			expect( getNodeBeforePosition( position, positionParent, textNode ) ).to.equal( li1 );
+		} );
+
+		// This util is covered with tests by Position#nodeBefore tests.
+	} );
 } );