diff --git a/_config/config.yml b/_config/config.yml
index 22543ce..483d40c 100644
--- a/_config/config.yml
+++ b/_config/config.yml
@@ -4,5 +4,11 @@ After:
   - gridfieldextensions
 ---
 
+SilverStripe\Core\Injector\Injector:
+  Psr\SimpleCache\CacheInterface.ListingsCache:
+    factory: SilverStripe\Core\Cache\CacheFactory
+    constructor:
+      namespace: "ListingsCache"
+
 Fromholdio\Listings\Forms\GridFieldListedPagesAddNewButton:
   showEmptyString: true
diff --git a/src/Extensions/ListedPageExtension.php b/src/Extensions/ListedPageExtension.php
index 56910c6..31b869c 100644
--- a/src/Extensions/ListedPageExtension.php
+++ b/src/Extensions/ListedPageExtension.php
@@ -13,11 +13,6 @@
 
 class ListedPageExtension extends SiteTreeExtension
 {
-    public static function add_to_class($class, $extensionClass, $args = null)
-    {
-        ListedPages::register_class($class);
-    }
-
     public function updateCMSFields(FieldList $fields)
     {
         // Remove ParentID dropdown (if mode != cmstree)
diff --git a/src/Extensions/ListingsRootPageExtension.php b/src/Extensions/ListingsRootPageExtension.php
index e58c970..28f74ec 100644
--- a/src/Extensions/ListingsRootPageExtension.php
+++ b/src/Extensions/ListingsRootPageExtension.php
@@ -77,11 +77,6 @@ class ListingsRootPageExtension extends ListingsSiteTreeExtension
      */
     private static $administration_mode = 'cmstree';
 
-    public static function add_to_class($class, $extensionClass, $args = null)
-    {
-        ListingsRoots::register_class($class);
-    }
-
     public function getListedPagesParentIDs()
     {
         return [$this->owner->ID];
diff --git a/src/ListedPages.php b/src/ListedPages.php
index deecdf8..8b66e48 100644
--- a/src/ListedPages.php
+++ b/src/ListedPages.php
@@ -4,33 +4,41 @@
 
 use Fromholdio\CommonAncestor\CommonAncestor;
 use Fromholdio\Listings\Extensions\ListedPageExtension;
+use Psr\SimpleCache\CacheInterface;
 use SilverStripe\CMS\Model\SiteTree;
+use SilverStripe\Control\Middleware\FlushMiddleware;
 use SilverStripe\Core\ClassInfo;
-use SilverStripe\Core\Config\Configurable;
 use SilverStripe\Core\Extensible;
+use SilverStripe\Core\Flushable;
+use SilverStripe\Core\Config\Configurable;
 use SilverStripe\Core\Injector\Injectable;
+use SilverStripe\Core\Injector\Injector;
 use SilverStripe\ORM\DataList;
 
-class ListedPages
+class ListedPages implements Flushable
 {
     use Injectable;
     use Extensible;
     use Configurable;
 
-    protected static $classes = [];
-
-    public static function register_class($class)
-    {
-        self::validate_class($class);
-        self::$classes[$class] = $class;
-    }
-
     public static function get_classes($includeSubclasses = true)
     {
-        $classes = self::$classes;
+        $classes = [];
+        
+        // retrieve classes from cache
+        $cache = self::get_cache();
+		$cacheKey = self::get_cache_key('Classes');
+		if (!$cache->has($cacheKey)) {
+		    self::build_cache();
+		}
+		if ($cache->has($cacheKey)) {
+		    $classes = $cache->get($cacheKey);
+        }
+        
         if ($includeSubclasses) {
             $classes = self::add_subclasses($classes);
         }
+        
         return $classes;
     }
 
@@ -51,7 +59,7 @@ public static function get_classes_dropdown_source($includeSubclasses = true, $u
 
     public static function get_index_classes()
     {
-        $classes = self::$classes;
+        $classes = self::get_classes();
         foreach ($classes as $class) {
             if (!$class::singleton()->config()->get('can_be_root')) {
                 unset($classes[$class]);
@@ -133,15 +141,27 @@ public static function get_common_class($classes = null)
 
     protected static function add_subclasses($classes)
     {
-        $classes = array_combine($classes, $classes);
-
-        foreach ($classes as $class) {
-            $subclasses = ClassInfo::subclassesFor($class);
-            foreach ($subclasses as $subclass) {
-                $classes[$subclass] = $subclass;
+        // retrieve classes from cache
+        $cache = self::get_cache();
+        $cacheKey = self::get_cache_key('IncludeSubclasses', $classes);
+        if ($cache->has($cacheKey)) {
+            
+            $classes = $cache->get($cacheKey);
+        
+        } else {
+        
+            $classes = array_combine($classes, $classes);
+    
+            foreach ($classes as $class) {
+                $subclasses = ClassInfo::subclassesFor($class);
+                foreach ($subclasses as $subclass) {
+                    $classes[$subclass] = $subclass;
+                }
             }
+            
+            $cache->set($cacheKey, $classes);
         }
-
+        
         return $classes;
     }
 
@@ -203,4 +223,42 @@ public static function validate_classes($classes)
 
         return true;
     }
+
+    /**
+     * This function is triggered early in the request if the "flush" query
+     * parameter has been set. Each class that implements Flushable implements
+     * this function which looks after it's own specific flushing functionality.
+     *
+     * @see FlushMiddleware
+     */
+    public static function flush()
+    {
+        self::get_cache()->clear();
+        self::build_cache();
+    }
+    
+    private static function build_cache() {
+        // build pages cache
+        $pages = [];
+        $classes = ClassInfo::subclassesFor(SiteTree::class);
+        foreach ($classes as $class) {
+            if ($class::has_extension(ListedPageExtension::class)) {
+                self::validate_class($class);
+                $pages[$class] = $class;
+            }
+        }
+        $cache = self::get_cache();
+        $cacheKey = self::get_cache_key('Classes');
+        $cache->set($cacheKey, $pages);
+        self::add_subclasses($pages);
+    }
+    
+    private static function get_cache() {
+        return Injector::inst()->get(CacheInterface::class . '.ListingsCache');
+    }
+    
+    private static function get_cache_key($suffix, $classes=null) {
+        return 'ListedPagesClasses-'.$suffix.($classes ? md5(implode('-', $classes)) : '');
+    }
+
 }
diff --git a/src/ListingsRoots.php b/src/ListingsRoots.php
index 581079e..8c7062e 100644
--- a/src/ListingsRoots.php
+++ b/src/ListingsRoots.php
@@ -2,33 +2,42 @@
 
 namespace Fromholdio\Listings;
 
+use Fromholdio\CommonAncestor\CommonAncestor;
 use Fromholdio\Listings\Extensions\ListingsRootPageExtension;
+use Psr\SimpleCache\CacheInterface;
 use SilverStripe\CMS\Model\SiteTree;
+use SilverStripe\Control\Middleware\FlushMiddleware;
 use SilverStripe\Core\ClassInfo;
-use SilverStripe\Core\Config\Configurable;
 use SilverStripe\Core\Extensible;
+use SilverStripe\Core\Flushable;
+use SilverStripe\Core\Config\Configurable;
 use SilverStripe\Core\Injector\Injectable;
+use SilverStripe\Core\Injector\Injector;
 
-class ListingsRoots
+class ListingsRoots implements Flushable
 {
     use Injectable;
     use Extensible;
     use Configurable;
 
-    protected static $classes = [];
-
-    public static function register_class($class)
-    {
-        self::validate_class($class);
-        self::$classes[$class] = $class;
-    }
-
     public static function get_classes($includeSubclasses = true)
     {
-        $classes = self::$classes;
+        $classes = [];
+        
+        // retrieve classes from cache
+        $cache = self::get_cache();
+        $cacheKey = self::get_cache_key('Classes');
+        if (!$cache->has($cacheKey)) {
+            self::build_cache();
+        }
+        if ($cache->has($cacheKey)) {
+            $classes = $cache->get($cacheKey);
+        }
+        
         if ($includeSubclasses) {
             $classes = self::add_subclasses($classes);
         }
+        
         return $classes;
     }
 
@@ -120,15 +129,28 @@ public static function get_common_plural_name($classes)
 
     protected static function add_subclasses($classes)
     {
-        $classes = array_combine($classes, $classes);
-
-        foreach ($classes as $class) {
-            $subclasses = ClassInfo::subclassesFor($class);
-            foreach ($subclasses as $subclass) {
-                $classes[$subclass] = $subclass;
+        $cache = self::get_cache();
+        
+        // retrieve classes from cache
+        $cacheKey = self::get_cache_key('IncludeSubclasses', $classes);
+        if ($cache->has($cacheKey)) {
+            
+            $classes = $cache->get($cacheKey);
+            
+        } else {
+            
+            $classes = array_combine($classes, $classes);
+            
+            foreach ($classes as $class) {
+                $subclasses = ClassInfo::subclassesFor($class);
+                foreach ($subclasses as $subclass) {
+                    $classes[$subclass] = $subclass;
+                }
             }
+            
+            $cache->set($cacheKey, $classes);
         }
-
+        
         return $classes;
     }
 
@@ -190,4 +212,41 @@ public static function validate_classes($classes)
 
         return true;
     }
+
+    /**
+     * This function is triggered early in the request if the "flush" query
+     * parameter has been set. Each class that implements Flushable implements
+     * this function which looks after it's own specific flushing functionality.
+     *
+     * @see FlushMiddleware
+     */
+    public static function flush()
+    {
+        self::get_cache()->clear();
+        self::build_cache();
+    }
+    
+    private static function build_cache() {
+        // build pages cache
+        $pages = [];
+        $classes = ClassInfo::subclassesFor(SiteTree::class);
+        foreach ($classes as $class) {
+            if ($class::has_extension(ListingsRootPageExtension::class)) {
+                self::validate_class($class);
+                $pages[$class] = $class;
+            }
+        }
+        $cache = self::get_cache();
+        $cacheKey = self::get_cache_key('Classes');
+        $cache->set($cacheKey, $pages);
+        self::add_subclasses($pages);
+    }
+    
+    private static function get_cache() {
+        return Injector::inst()->get(CacheInterface::class . '.ListingsCache');
+    }
+    
+    private static function get_cache_key($suffix, $classes=null) {
+        return 'ListingsRootClasses-'.$suffix.($classes ? md5(implode('-', $classes)) : '');
+    }
 }