diff --git a/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageSortedSet.php b/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageSortedSet.php
index c01196c..a7ce599 100644
--- a/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageSortedSet.php
+++ b/core/lib/Drupal/Core/KeyValueStore/DatabaseStorageSortedSet.php
@@ -14,26 +14,36 @@
 class DatabaseStorageSortedSet implements KeyValueStoreSortedSetInterface {
 
   /**
+   * The name of the collection holding key and value pairs.
+   *
    * @var string
    */
   protected $collection;
 
   /**
+   * The serialization class to use.
+   *
    * @var \Drupal\Component\Serialization\SerializationInterface
    */
   protected $serializer;
 
   /**
+   * The database connection to use.
+   *
    * @var \Drupal\Core\Database\Connection
    */
   protected $connection;
 
   /**
+   * The name of the SQL table to use, defaults to key_value_sorted.
+   *
    * @var string
    */
   protected $table;
 
   /**
+   * Constructs the database key/value implementation for sorted sets.
+   *
    * @param string $collection
    *   The name of the collection holding key and value pairs.
    * @param \Drupal\Component\Serialization\SerializationInterface $serializer
@@ -54,8 +64,7 @@ public function __construct($collection, SerializationInterface $serializer, Con
    * {@inheritdoc}
    */
   public function add($score, $member) {
-    $this->addMultiple(array(array($score => $member)));
-    return $this;
+    return $this->addMultiple([[$score => $member]]);
   }
 
   /**
@@ -66,11 +75,11 @@ public function addMultiple(array $pairs) {
       foreach ($pair as $score => $member) {
         $encoded_member = $this->serializer->encode($member);
         $this->connection->merge($this->table)
-          ->fields(array(
+          ->fields([
             'collection' => $this->collection,
             'name' => $score,
             'value' => $encoded_member,
-          ))
+          ])
           ->condition('collection', $this->collection)
           ->condition('value', $encoded_member)
           ->execute();
@@ -84,8 +93,8 @@ public function addMultiple(array $pairs) {
    */
   public function getCount() {
     return $this->connection->select($this->table, 't')
-      ->condition('collection', $this->collection)
       ->countQuery()
+      ->condition('collection', $this->collection)
       ->execute()
       ->fetchField();
   }
@@ -95,17 +104,17 @@ public function getCount() {
    */
   public function getRange($start, $stop = NULL) {
     $query = $this->connection->select($this->table, 't')
-      ->fields('t', array('value'))
+      ->fields('t', ['value'])
+      ->orderBy('name', 'ASC')
       ->condition('collection', $this->collection)
       ->condition('name', $start, '>=');
 
-    if ($stop !== NULL) {
+    if (is_int($stop)) {
       $query->condition('name', $stop, '<=');
     }
-    $result = $query->orderBy('name', 'ASC')->execute();
 
-    $values = array();
-    foreach ($result as $item) {
+    $values = [];
+    foreach ($query->execute() as $item) {
       $values[] = $this->serializer->decode($item->value);
     }
     return $values;
diff --git a/core/lib/Drupal/Core/KeyValueStore/KeyValueStoreSortedSetInterface.php b/core/lib/Drupal/Core/KeyValueStore/KeyValueStoreSortedSetInterface.php
index 98d9181..eed1ee8 100644
--- a/core/lib/Drupal/Core/KeyValueStore/KeyValueStoreSortedSetInterface.php
+++ b/core/lib/Drupal/Core/KeyValueStore/KeyValueStoreSortedSetInterface.php
@@ -11,7 +11,9 @@
 interface KeyValueStoreSortedSetInterface {
 
   /**
-   * @param float $score
+   * Add a single item to a set.
+   *
+   * @param int $score
    *   The key for the item, for example microtime(), which can be used to
    *   generate a sequential value.
    * @param mixed $member
@@ -22,6 +24,8 @@
   public function add($score, $member);
 
   /**
+   * Add multiple items to a set.
+   *
    * @param array $pairs
    *   An array of key/value pairs to add.
    *
@@ -30,27 +34,35 @@ public function add($score, $member);
   public function addMultiple(array $pairs);
 
   /**
-   * @return float
+   * Get the highest key in a set.
+   *
+   * @return int
    *   The highest key in the collection.
    */
   public function getMaxScore();
 
   /**
-   * @return float
+   * Get the lowest key in in a set.
+   *
+   * @return int
    *   The lowest key in the collection.
    */
   public function getMinScore();
 
   /**
-   * @return integer
+   * Get the number of items in a collection.
+   *
+   * @return int
    *   The number of items in a collection.
    */
   public function getCount();
 
   /**
-   * @param float $start
+   * Get multiple items within a range of keys.
+   *
+   * @param int $start
    *   The first key in the range.
-   * @param float $stop
+   * @param int $stop
    *   The last key in the range.
    *
    * @return array
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 5676fee..22df38e 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -994,7 +994,7 @@ function system_schema() {
   );
 
   $schema['key_value_sorted'] = array(
-    'description' => 'Key-value list storage table.',
+    'description' => 'Sorted key-value list storage table.',
     'fields' => array(
       'collection' => array(
         'description' => 'A named collection of key and value pairs.',
@@ -1836,7 +1836,7 @@ function system_update_8203() {
  */
 function system_update_8300() {
   $table = array(
-    'description' => 'Key-value list storage table.',
+    'description' => 'Sorted key-value list storage table.',
     'fields' => array(
       'collection' => array(
         'description' => 'A named collection of key and value pairs.',
@@ -1848,7 +1848,7 @@ function system_update_8300() {
       // KEY is an SQL reserved word, so use 'name' as the key's field name.
       'name' => array(
         'description' => 'The index or score key for the value.',
-        'type' => 'float',
+        'type' => 'int',
         'not null' => TRUE,
         'default' => 0,
         'size' => 'big',
diff --git a/core/tests/Drupal/KernelTests/Core/KeyValueStore/DatabaseStorageSortedSetTest.php b/core/tests/Drupal/KernelTests/Core/KeyValueStore/DatabaseStorageSortedSetTest.php
index d06d2eb..4d0fd73 100644
--- a/core/tests/Drupal/KernelTests/Core/KeyValueStore/DatabaseStorageSortedSetTest.php
+++ b/core/tests/Drupal/KernelTests/Core/KeyValueStore/DatabaseStorageSortedSetTest.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\KernelTests\Core\KeyValueStore;
 
+use Drupal\Core\Database\DatabaseExceptionWrapper;
 use Drupal\KernelTests\KernelTestBase;
 
 /**
@@ -34,9 +35,12 @@ class DatabaseStorageSortedSetTest extends KernelTestBase {
    */
   protected $store;
 
+  /**
+   * {@inheritdoc}
+   */
   public function setUp() {
     parent::setUp();
-    $this->installSchema('system', array('key_value_sorted'));
+    $this->installSchema('system', ['key_value_sorted']);
 
     $this->collection = $this->randomMachineName();
     $this->serializer = \Drupal::service('serialization.phpserialize');
@@ -44,9 +48,15 @@ public function setUp() {
     $this->store = \Drupal::service('keyvalue.sorted_set')->get($this->collection);
   }
 
-  public function assertPairs($expected_pairs) {
+  /**
+   * Helper method to assert key value pairs.
+   *
+   * @param $expected_pairs array
+   *   Array of expected key value pairs.
+   */
+  public function assertPairs(array $expected_pairs) {
     $result = $this->connection->select('key_value_sorted', 't')
-      ->fields('t', array('name', 'value'))
+      ->fields('t', ['name', 'value'])
       ->condition('collection', $this->collection)
       ->condition('name', array_keys($expected_pairs), 'IN')
       ->execute()
@@ -59,6 +69,14 @@ public function assertPairs($expected_pairs) {
     }
   }
 
+  /**
+   * Helper method to assert the number of records.
+   *
+   * @param $expected int
+   *   Expected number of records.
+   * @param null $message string
+   *   The message to display.
+   */
   public function assertRecords($expected, $message = NULL) {
     $count = $this->connection->select('key_value_sorted', 't')
       ->fields('t')
@@ -69,10 +87,19 @@ public function assertRecords($expected, $message = NULL) {
     $this->assertEquals($expected, $count, $message ? $message : "There are $expected records.");
   }
 
+  /**
+   * Helper method to generate a key based on microtime().
+   *
+   * @return integer
+   *   A key based on microtime().
+   */
   public function newKey() {
     return (int) (microtime(TRUE) * 1000000);
   }
 
+  /**
+   * Tests getting and setting of sorted key value sets.
+   */
   public function testCalls() {
     $key0 = $this->newKey();
     $value0 = $this->randomMachineName();