diff --git a/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php b/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php
index b21958b752c..0ce499caff6 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php
@@ -1454,6 +1454,14 @@ class ContentEntityDatabaseStorage extends ContentEntityStorageBase implements S
       $current['fields'][$real_name] = $attributes;
     }
 
+    // Add unique keys.
+    foreach ($schema['unique keys'] as $unique_key_name => $columns) {
+      $real_name = static::_fieldIndexName($field, $unique_key_name);
+      foreach ($columns as $column_name) {
+        $current['unique keys'][$real_name][] = static::_fieldColumnName($field, $column_name);
+      }
+    }
+
     // Add indexes.
     foreach ($schema['indexes'] as $index_name => $columns) {
       $real_name = static::_fieldIndexName($field, $index_name);
diff --git a/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaHandler.php b/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaHandler.php
index 5e7c0e511ad..22947946e0d 100644
--- a/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaHandler.php
+++ b/core/lib/Drupal/Core/Entity/Schema/ContentEntitySchemaHandler.php
@@ -325,13 +325,6 @@ class ContentEntitySchemaHandler implements EntitySchemaHandlerInterface {
       'foreign keys' => array(),
     );
 
-    if ($this->entityType->hasKey('uuid')) {
-      $uuid_key = $this->entityType->getKey('uuid');
-      $schema['unique keys'] = array(
-        $this->getEntityIndexName($uuid_key) => array($uuid_key),
-      );
-    }
-
     if ($this->entityType->hasKey('revision')) {
       $revision_key = $this->entityType->getKey('revision');
       $key_name = $this->getEntityIndexName($revision_key);
@@ -342,6 +335,8 @@ class ContentEntitySchemaHandler implements EntitySchemaHandlerInterface {
       );
     }
 
+    $this->addTableDefaults($schema);
+
     return $schema;
   }
 
@@ -370,6 +365,8 @@ class ContentEntitySchemaHandler implements EntitySchemaHandlerInterface {
 
     $schema['indexes'][$this->getEntityIndexName($id_key)] = array($id_key);
 
+    $this->addTableDefaults($schema);
+
     return $schema;
   }
 
@@ -402,6 +399,8 @@ class ContentEntitySchemaHandler implements EntitySchemaHandlerInterface {
       $schema['indexes'][$this->getEntityIndexName($key)] = array($key);
     }
 
+    $this->addTableDefaults($schema);
+
     return $schema;
   }
 
@@ -434,9 +433,26 @@ class ContentEntitySchemaHandler implements EntitySchemaHandlerInterface {
       ),
     );
 
+    $this->addTableDefaults($schema);
+
     return $schema;
   }
 
+  /**
+   * Adds defaults to a table schema definition.
+   *
+   * @param $schema
+   *   The schema definition array for a single table, passed by reference.
+   */
+  protected function addTableDefaults(&$schema) {
+    $schema += array(
+      'fields' => array(),
+      'unique keys' => array(),
+      'indexes' => array(),
+      'foreign keys' => array(),
+    );
+  }
+
   /**
    * Processes the gathered schema for a base table.
    *
diff --git a/core/lib/Drupal/Core/Field/FieldDefinition.php b/core/lib/Drupal/Core/Field/FieldDefinition.php
index cfeccf850c7..c6a661e4e45 100644
--- a/core/lib/Drupal/Core/Field/FieldDefinition.php
+++ b/core/lib/Drupal/Core/Field/FieldDefinition.php
@@ -480,6 +480,7 @@ class FieldDefinition extends ListDataDefinition implements FieldDefinitionInter
       // Fill in default values.
       $schema += array(
         'columns' => array(),
+        'unique keys' => array(),
         'indexes' => array(),
         'foreign keys' => array(),
       );
diff --git a/core/lib/Drupal/Core/Field/FieldItemInterface.php b/core/lib/Drupal/Core/Field/FieldItemInterface.php
index d10790dc819..3943bad553c 100644
--- a/core/lib/Drupal/Core/Field/FieldItemInterface.php
+++ b/core/lib/Drupal/Core/Field/FieldItemInterface.php
@@ -69,6 +69,8 @@ interface FieldItemInterface extends ComplexDataInterface {
    *     definitions depend on field settings when possible. No assumptions
    *     should be made on how storage engines internally use the original
    *     column name to structure their storage.
+   *   - unique keys: (optional) An array of Schema API unique key definitions.
+   *     Only columns that appear in the 'columns' array are allowed.
    *   - indexes: (optional) An array of Schema API index definitions. Only
    *     columns that appear in the 'columns' array are allowed. Those indexes
    *     will be used as default indexes. Callers of field_create_field() can
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
index 15cbe745be9..50df9bb3558 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UuidItem.php
@@ -7,6 +7,8 @@
 
 namespace Drupal\Core\Field\Plugin\Field\FieldType;
 
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+
 /**
  * Defines the 'uuid' entity field type.
  *
@@ -39,4 +41,14 @@ class UuidItem extends StringItem {
     $this->setValue(array('value' => $uuid->generate()), $notify);
     return $this;
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function schema(FieldStorageDefinitionInterface $field_definition) {
+    $schema = parent::schema($field_definition);
+    $schema['unique keys']['value'] = array('value');
+    return $schema;
+  }
+
 }
diff --git a/core/modules/field/src/Entity/FieldConfig.php b/core/modules/field/src/Entity/FieldConfig.php
index 29f22a34c03..f25af7bacc2 100644
--- a/core/modules/field/src/Entity/FieldConfig.php
+++ b/core/modules/field/src/Entity/FieldConfig.php
@@ -456,7 +456,11 @@ class FieldConfig extends ConfigEntityBase implements FieldConfigInterface {
       $class = $this->getFieldItemClass();
       $schema = $class::schema($this);
       // Fill in default values for optional entries.
-      $schema += array('indexes' => array(), 'foreign keys' => array());
+      $schema += array(
+        'unique keys' => array(),
+        'indexes' => array(),
+        'foreign keys' => array(),
+      );
 
       // Check that the schema does not include forbidden column names.
       if (array_intersect(array_keys($schema['columns']), static::getReservedColumns())) {
diff --git a/core/modules/field/src/Tests/TestItemTest.php b/core/modules/field/src/Tests/TestItemTest.php
index f48c48cc558..a7680d31899 100644
--- a/core/modules/field/src/Tests/TestItemTest.php
+++ b/core/modules/field/src/Tests/TestItemTest.php
@@ -94,6 +94,7 @@ class TestItemTest extends FieldUnitTestBase {
           'not null' => FALSE,
         ),
       ),
+      'unique keys' => array(),
       'indexes' => array(
         'value' => array('value'),
       ),
diff --git a/core/tests/Drupal/Tests/Core/Entity/ContentEntityDatabaseStorageTest.php b/core/tests/Drupal/Tests/Core/Entity/ContentEntityDatabaseStorageTest.php
index cc77d6d6bd0..fc095b5d792 100644
--- a/core/tests/Drupal/Tests/Core/Entity/ContentEntityDatabaseStorageTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/ContentEntityDatabaseStorageTest.php
@@ -291,6 +291,7 @@ class ContentEntityDatabaseStorageTest extends UnitTestCase {
           ),
         ),
         'primary key' => array('id'),
+        'unique keys' => array(),
         'indexes' => array(),
         'foreign keys' => array(),
       ),
@@ -973,6 +974,7 @@ class ContentEntityDatabaseStorageTest extends UnitTestCase {
           'not null' => FALSE,
         ),
       ),
+      'unique keys' => array(),
       'indexes' => array(),
       'foreign keys' => array(),
     );
diff --git a/core/tests/Drupal/Tests/Core/Entity/Schema/ContentEntitySchemaHandlerTest.php b/core/tests/Drupal/Tests/Core/Entity/Schema/ContentEntitySchemaHandlerTest.php
index b39fbcbc29a..8fac217b35d 100644
--- a/core/tests/Drupal/Tests/Core/Entity/Schema/ContentEntitySchemaHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Entity/Schema/ContentEntitySchemaHandlerTest.php
@@ -95,13 +95,11 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
   /**
    * Tests the schema for non-revisionable, non-translatable entities.
    *
-   * @param bool $uuid_key
-   *   Whether or not the tested entity type should have a UUID key.
-   *
    * @covers ::__construct()
    * @covers ::getSchema()
    * @covers ::getTables()
    * @covers ::initializeBaseTable()
+   * @covers ::addTableDefaults()
    * @covers ::getEntityIndexName()
    * @covers ::addFieldSchema()
    * @covers ::getFieldIndexes()
@@ -111,16 +109,11 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
    * @covers ::addDefaultLangcodeSchema()
    * @covers ::processBaseTable()
    * @covers ::processIdentifierSchema()
-   *
-   * @dataProvider providerTestGetSchemaLayoutBase
    */
-  public function testGetSchemaBase($uuid_key) {
+  public function testGetSchemaBase() {
     $this->entityType = new ContentEntityType(array(
       'id' => 'entity_test',
-      'entity_keys' => array(
-        'id' => 'id',
-        'uuid' => $uuid_key ? 'uuid' : NULL,
-      ),
+      'entity_keys' => array('id' => 'id'),
     ));
 
     // Add a field with a 'length' constraint.
@@ -132,16 +125,6 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
         ),
       ),
     ));
-    if ($uuid_key) {
-      $this->setUpStorageDefinition('uuid', array(
-        'columns' => array(
-          'value' => array(
-            'type' => 'varchar',
-            'length' => 128,
-          ),
-        ),
-      ));
-    }
     // Add a multi-column field.
     $this->setUpStorageDefinition('description', array(
       'columns' => array(
@@ -155,11 +138,51 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
         ),
       ),
     ));
+    // Add a field with a unique key.
+    $this->setUpStorageDefinition('uuid', array(
+      'columns' => array(
+        'value' => array(
+          'type' => 'varchar',
+          'length' => 128,
+        ),
+      ),
+      'unique keys' => array(
+        'value' => array('value'),
+      ),
+    ));
+    // Add a field with a unique key, specified as column name and length.
+    $this->setUpStorageDefinition('hash', array(
+      'columns' => array(
+        'value' => array(
+          'type' => 'varchar',
+          'length' => 20,
+        ),
+      ),
+      'unique keys' => array(
+        'value' => array(array('value', 10)),
+      ),
+    ));
+    // Add a field with a multi-column unique key.
+    $this->setUpStorageDefinition('email', array(
+      'columns' => array(
+        'username' => array(
+          'type' => 'varchar',
+        ),
+        'hostname' => array(
+          'type' => 'varchar',
+        ),
+        'domain' => array(
+          'type' => 'varchar',
+        )
+      ),
+      'unique keys' => array(
+        'email' => array('username', 'hostname', array('domain', 3)),
+      ),
+    ));
     // Add a field with an index.
     $this->setUpStorageDefinition('owner', array(
       'columns' => array(
         'target_id' => array(
-          'description' => 'The ID of the target entity.',
           'type' => 'int',
         ),
       ),
@@ -171,7 +194,6 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
     $this->setUpStorageDefinition('translator', array(
       'columns' => array(
         'target_id' => array(
-          'description' => 'The ID of the target entity.',
           'type' => 'int',
         ),
       ),
@@ -260,6 +282,28 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
             'description' => 'The description field.',
             'type' => 'varchar',
           ),
+          'uuid' => array(
+            'description' => 'The uuid field.',
+            'type' => 'varchar',
+            'length' => 128,
+          ),
+          'hash' => array(
+            'description' => 'The hash field.',
+            'type' => 'varchar',
+            'length' => 20,
+          ),
+          'email__username' => array(
+            'description' => 'The email field.',
+            'type' => 'varchar',
+          ),
+          'email__hostname' => array(
+            'description' => 'The email field.',
+            'type' => 'varchar',
+          ),
+          'email__domain' => array(
+            'description' => 'The email field.',
+            'type' => 'varchar',
+          ),
           'owner' => array(
             'description' => 'The owner field.',
             'type' => 'int',
@@ -301,6 +345,15 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           ),
         ),
         'primary key' => array('id'),
+        'unique keys' => array(
+          'entity_test_field__uuid__value' => array('uuid'),
+          'entity_test_field__hash__value' => array(array('hash', 10)),
+          'entity_test_field__email__email' => array(
+            'email__username',
+            'email__hostname',
+            array('email__domain', 3),
+          ),
+        ),
         'indexes' => array(
           'entity_test_field__owner__target_id' => array('owner'),
           'entity_test_field__translator__target_id' => array(
@@ -324,35 +377,11 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
         ),
       ),
     );
-    if ($uuid_key) {
-      $expected['entity_test']['fields']['uuid'] = array(
-        'type' => 'varchar',
-        'length' => 128,
-        'description' => 'The uuid field.',
-        'not null' => TRUE,
-      );
-      $expected['entity_test']['unique keys']['entity_test__uuid'] = array('uuid');
-    }
     $actual = $this->schemaHandler->getSchema();
 
     $this->assertEquals($expected, $actual);
   }
 
-  /**
-   * Provides data for testGetSchemaLayoutBase().
-   *
-   * @return array
-   *   Returns a nested array where each inner array returns a boolean,
-   *   indicating whether or not the tested entity type should include a UUID
-   *   key.
-   */
-  public function providerTestGetSchemaLayoutBase() {
-    return array(
-      array(FALSE),
-      array(TRUE),
-    );
-  }
-
   /**
    * Tests the schema for revisionable, non-translatable entities.
    *
@@ -361,6 +390,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
    * @covers ::getTables()
    * @covers ::initializeBaseTable()
    * @covers ::initializeRevisionTable()
+   * @covers ::addTableDefaults()
    * @covers ::getEntityIndexName()
    * @covers ::processRevisionTable()
    * @covers ::processIdentifierSchema()
@@ -411,6 +441,9 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           )
         ),
         'primary key' => array('id'),
+        'unique keys' => array(
+          'entity_test__revision_id' => array('revision_id'),
+        ),
         'indexes' => array(),
         'foreign keys' => array(
           'entity_test__revision' => array(
@@ -418,9 +451,6 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
             'columns' => array('revision_id' => 'revision_id'),
           )
         ),
-        'unique keys' => array(
-          'entity_test__revision_id' => array('revision_id'),
-        ),
       ),
       'entity_test_revision' => array(
         'description' => 'The revision table for entity_test entities.',
@@ -436,6 +466,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           ),
         ),
         'primary key' => array('revision_id'),
+        'unique keys' => array(),
         'indexes' => array(
           'entity_test__id' => array('id'),
         ),
@@ -460,6 +491,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
    * @covers ::getSchema()
    * @covers ::getTables()
    * @covers ::initializeDataTable()
+   * @covers ::addTableDefaults()
    * @covers ::getEntityIndexName()
    * @covers ::processDataTable()
    */
@@ -509,6 +541,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           )
         ),
         'primary key' => array('id'),
+        'unique keys' => array(),
         'indexes' => array(),
         'foreign keys' => array(),
       ),
@@ -527,6 +560,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           ),
         ),
         'primary key' => array('id', 'langcode'),
+        'unique keys' => array(),
         'indexes' => array(),
         'foreign keys' => array(
           'entity_test' => array(
@@ -549,6 +583,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
    * @covers ::getSchema()
    * @covers ::getTables()
    * @covers ::initializeDataTable()
+   * @covers ::addTableDefaults()
    * @covers ::getEntityIndexName()
    * @covers ::initializeRevisionDataTable()
    * @covers ::processRevisionDataTable()
@@ -619,10 +654,10 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           )
         ),
         'primary key' => array('id'),
-        'indexes' => array(),
         'unique keys' => array(
           'entity_test__revision_id' => array('revision_id'),
         ),
+        'indexes' => array(),
         'foreign keys' => array(
           'entity_test__revision' => array(
             'table' => 'entity_test_revision',
@@ -649,6 +684,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           ),
         ),
         'primary key' => array('revision_id'),
+        'unique keys' => array(),
         'indexes' => array(
           'entity_test__id' => array('id'),
         ),
@@ -678,6 +714,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           ),
         ),
         'primary key' => array('id', 'langcode'),
+        'unique keys' => array(),
         'indexes' => array(
           'entity_test__revision_id' => array('revision_id'),
         ),
@@ -707,6 +744,7 @@ class ContentEntitySchemaHandlerTest extends UnitTestCase {
           ),
         ),
         'primary key' => array('revision_id', 'langcode'),
+        'unique keys' => array(),
         'indexes' => array(),
         'foreign keys' => array(
           'entity_test' => array(