diff --git a/search_api.install b/search_api.install
index 06fa6071..3bef1f10 100644
--- a/search_api.install
+++ b/search_api.install
@@ -57,6 +57,16 @@ function search_api_schema() {
 }
 
 /**
+ * Implements hook_uninstall().
+ */
+function search_api_uninstall() {
+  \Drupal::state()->delete('search_api_use_tracking_batch');
+  foreach (\Drupal::configFactory()->listAll('search_api.index.') as $index_id) {
+    \Drupal::state()->delete("search_api.index.$index_id.has_reindexed");
+  }
+}
+
+/**
  * Implements hook_requirements().
  */
 function search_api_requirements($phase) {
diff --git a/search_api.routing.yml b/search_api.routing.yml
index 34c34480..bd5c2a93 100644
--- a/search_api.routing.yml
+++ b/search_api.routing.yml
@@ -30,6 +30,10 @@ entity.search_api_server.canonical:
     _title: "View"
   requirements:
     _entity_access: 'search_api_server.view'
+  options:
+    parameters:
+      search_api_server:
+        with_config_overrides: TRUE
 
 entity.search_api_server.edit_form:
   path: '/admin/config/search/search-api/server/{search_api_server}/edit'
@@ -44,6 +48,10 @@ entity.search_api_server.delete_form:
     _entity_form: 'search_api_server.delete'
   requirements:
     _entity_access: 'search_api_server.delete'
+  options:
+    parameters:
+      search_api_server:
+        with_config_overrides: TRUE
 
 entity.search_api_server.enable:
   path: '/admin/config/search/search-api/server/{search_api_server}/enable'
@@ -52,6 +60,10 @@ entity.search_api_server.enable:
   requirements:
     _entity_access: 'search_api_server.enable'
     _csrf_token: 'TRUE'
+  options:
+    parameters:
+      search_api_server:
+        with_config_overrides: TRUE
 
 entity.search_api_server.disable:
   path: '/admin/config/search/search-api/server/{search_api_server}/disable'
@@ -59,6 +71,10 @@ entity.search_api_server.disable:
     _entity_form: 'search_api_server.disable'
   requirements:
     _entity_access: 'search_api_server.disable'
+  options:
+    parameters:
+      search_api_server:
+        with_config_overrides: TRUE
 
 entity.search_api_server.clear:
   path: '/admin/config/search/search-api/server/{search_api_server}/clear'
@@ -66,6 +82,10 @@ entity.search_api_server.clear:
     _entity_form: 'search_api_server.clear'
   requirements:
     _entity_access: 'search_api_server.clear'
+  options:
+    parameters:
+      search_api_server:
+        with_config_overrides: TRUE
 
 entity.search_api_index.add_form:
   path: '/admin/config/search/search-api/add-index'
@@ -81,6 +101,10 @@ entity.search_api_index.canonical:
     _title_callback: '\Drupal\search_api\Controller\IndexController::pageTitle'
   requirements:
     _entity_access: 'search_api_index.view'
+  options:
+    parameters:
+      search_api_index:
+        with_config_overrides: TRUE
 
 entity.search_api_index.edit_form:
   path: '/admin/config/search/search-api/index/{search_api_index}/edit'
@@ -95,6 +119,10 @@ entity.search_api_index.delete_form:
     _entity_form: 'search_api_index.delete'
   requirements:
     _entity_access: 'search_api_index.delete'
+  options:
+    parameters:
+      search_api_index:
+        with_config_overrides: TRUE
 
 entity.search_api_index.enable:
   path: '/admin/config/search/search-api/index/{search_api_index}/enable'
@@ -103,6 +131,10 @@ entity.search_api_index.enable:
   requirements:
     _entity_access: 'search_api_index.enable'
     _csrf_token: 'TRUE'
+  options:
+    parameters:
+      search_api_index:
+        with_config_overrides: TRUE
 
 entity.search_api_index.disable:
   path: '/admin/config/search/search-api/index/{search_api_index}/disable'
@@ -110,6 +142,10 @@ entity.search_api_index.disable:
     _entity_form: 'search_api_index.disable'
   requirements:
     _entity_access: 'search_api_index.disable'
+  options:
+    parameters:
+      search_api_index:
+        with_config_overrides: TRUE
 
 entity.search_api_index.fields:
   path: '/admin/config/search/search-api/index/{search_api_index}/fields'
@@ -182,6 +218,10 @@ entity.search_api_index.reindex:
     _entity_form: 'search_api_index.reindex'
   requirements:
     _entity_access: 'search_api_index.reindex'
+  options:
+    parameters:
+      search_api_index:
+        with_config_overrides: TRUE
 
 entity.search_api_index.clear:
   path: '/admin/config/search/search-api/index/{search_api_index}/clear'
@@ -189,3 +229,7 @@ entity.search_api_index.clear:
     _entity_form: 'search_api_index.clear'
   requirements:
     _entity_access: 'search_api_index.clear'
+  options:
+    parameters:
+      search_api_index:
+        with_config_overrides: TRUE
diff --git a/src/Backend/BackendInterface.php b/src/Backend/BackendInterface.php
index 1ef2424f..ad802db5 100644
--- a/src/Backend/BackendInterface.php
+++ b/src/Backend/BackendInterface.php
@@ -51,6 +51,10 @@ public function postInsert();
    *
    * The server's $original property can be used to inspect the old
    * configuration values.
+   *
+   * Take care, though, that the server at this point might be override-free and
+   * thus contain property values (and apparent changes) which will not really
+   * go into effect. The same goes for the If this might be the
    */
   public function preUpdate();
 
diff --git a/src/Entity/Index.php b/src/Entity/Index.php
index bbe53e78..83bb126e 100644
--- a/src/Entity/Index.php
+++ b/src/Entity/Index.php
@@ -37,7 +37,7 @@
  *     plural = "@count search indexes",
  *   ),
  *   handlers = {
- *     "storage" = "Drupal\Core\Config\Entity\ConfigEntityStorage",
+ *     "storage" = "Drupal\search_api\Entity\SearchApiConfigEntityStorage",
  *     "list_builder" = "Drupal\search_api\IndexListBuilder",
  *     "form" = {
  *       "default" = "Drupal\search_api\Form\IndexForm",
@@ -259,13 +259,6 @@ class Index extends ConfigEntityBase implements IndexInterface {
   protected $processorInstances;
 
   /**
-   * Whether reindexing has been triggered for this index in this page request.
-   *
-   * @var bool
-   */
-  protected $hasReindexed = FALSE;
-
-  /**
    * The number of currently active "batch tracking" modes.
    *
    * @var int
@@ -568,9 +561,9 @@ public function getProcessors() {
   /**
    * {@inheritdoc}
    */
-  public function getProcessorsByStage($stage) {
-    // Get a list of all processors meeting the criteria (stage and, optionally,
-    // enabled) along with their effective weights (user-set or default).
+  public function getProcessorsByStage($stage, $overrides = []) {
+    // Get a list of all processors which support this stage, along with their
+    // weights.
     $processors = $this->getProcessors();
     $processor_weights = array();
     foreach ($processors as $name => $processor) {
@@ -579,6 +572,16 @@ public function getProcessorsByStage($stage) {
       }
     }
 
+    // Apply any overrides that were passed by the caller.
+    foreach ($overrides as $name => $settings) {
+      /** @var \Drupal\search_api\Processor\ProcessorInterface $processor */
+      $processor = $this->createPlugin('processor', $name, $settings);
+      if ($processor->supportsStage($stage)) {
+        $processors[$name] = $processor;
+        $processor_weights[$name] = $processor->getWeight($stage);
+      }
+    }
+
     // Sort requested processors by weight.
     asort($processor_weights);
 
@@ -818,6 +821,14 @@ public function getFieldRenames() {
   /**
    * {@inheritdoc}
    */
+  public function discardFieldChanges() {
+    $this->fieldInstances = NULL;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function getPropertyDefinitions($datasource_id) {
     if (isset($datasource_id)) {
       $datasource = $this->getDatasource($datasource_id);
@@ -978,7 +989,7 @@ public function indexSpecificItems(array $search_objects) {
       }
       // Since we've indexed items now, triggering reindexing would have some
       // effect again. Therefore, we reset the flag.
-      $this->hasReindexed = FALSE;
+      $this->setHasReindexed(FALSE);
       \Drupal::moduleHandler()->invokeAll('search_api_items_indexed', array($this, $processed_ids));
     }
 
@@ -1084,8 +1095,8 @@ public function trackItemsDeleted($datasource_id, array $ids) {
    * {@inheritdoc}
    */
   public function reindex() {
-    if ($this->status() && !$this->hasReindexed) {
-      $this->hasReindexed = TRUE;
+    if ($this->status() && !$this->isReindexing()) {
+      $this->setHasReindexed();
       $this->getTrackerInstance()->trackAllItemsUpdated();
       \Drupal::moduleHandler()->invokeAll('search_api_index_reindex', array($this, FALSE));
     }
@@ -1098,9 +1109,9 @@ public function clear() {
     if ($this->status()) {
       // Only invoke the hook if we actually did something.
       $invoke_hook = FALSE;
-      if (!$this->hasReindexed) {
+      if (!$this->isReindexing()) {
         $invoke_hook = TRUE;
-        $this->hasReindexed = TRUE;
+        $this->setHasReindexed();
         $this->getTrackerInstance()->trackAllItemsUpdated();
       }
       if (!$this->isReadOnly()) {
@@ -1117,7 +1128,23 @@ public function clear() {
    * {@inheritdoc}
    */
   public function isReindexing() {
-    return $this->hasReindexed;
+    $id = $this->id();
+    return \Drupal::state()->get("search_api.index.$id.has_reindexed", FALSE);
+  }
+
+  /**
+   * Sets whether this index has all items marked for re-indexing.
+   *
+   * @param bool $has_reindexed
+   *   (optional) TRUE if the index has all items marked for re-indexing, FALSE
+   *   otherwise.
+   *
+   * @return $this
+   */
+  protected function setHasReindexed($has_reindexed = TRUE) {
+    $id = $this->id();
+    \Drupal::state()->set("search_api.index.$id.has_reindexed", $has_reindexed);
+    return $this;
   }
 
   /**
@@ -1155,9 +1182,26 @@ public function preSave(EntityStorageInterface $storage) {
       return;
     }
 
-    // Prevent enabling of indexes when the server is disabled.
-    if ($this->status() && !$this->isServerEnabled()) {
-      $this->disable();
+    // Retrieve active config overrides for this index.
+    $overrides = Utility::getConfigOverrides($this);
+
+    // Prevent enabling of indexes when the server is disabled. Take into
+    // account that both the index's "status" and "server" properties might be
+    // overridden.
+    if ($this->status() && !isset($overrides['status'])) {
+      // NULL would be a valid override, so we can't use isset() here.
+      if (!array_key_exists('server', $overrides)) {
+        if ($this->isServerEnabled()) {
+          $this->disable();
+        }
+      }
+      else {
+        $server_id = $overrides['server'];
+        $server = $server_id ? Server::load($server_id) : NULL;
+        if (!$server || !$server->status()) {
+          $this->disable();
+        }
+      }
     }
 
     // Merge in default options.
@@ -1190,7 +1234,8 @@ public function preSave(EntityStorageInterface $storage) {
     }
 
     // Call the preIndexSave() method of all applicable processors.
-    foreach ($this->getProcessorsByStage(ProcessorInterface::STAGE_PRE_INDEX_SAVE) as $processor) {
+    $processor_overrides = !empty($overrides['processor_settings']) ? $overrides['processor_settings'] : [];
+    foreach ($this->getProcessorsByStage(ProcessorInterface::STAGE_PRE_INDEX_SAVE, $processor_overrides) as $processor) {
       $processor->preIndexSave();
     }
 
@@ -1252,6 +1297,11 @@ protected function writeChangesToSettings() {
   public function postSave(EntityStorageInterface $storage, $update = TRUE) {
     parent::postSave($storage, $update);
 
+    // New indexes don't have any items indexed.
+    if (!$update) {
+      $this->setHasReindexed();
+    }
+
     try {
       // Fake an original for inserts to make code cleaner.
       /** @var \Drupal\search_api\IndexInterface $original */
@@ -1306,9 +1356,6 @@ public function postSave(EntityStorageInterface $storage, $update = TRUE) {
     catch (SearchApiException $e) {
       $this->logException($e);
     }
-
-    // Reset the field instances so saved renames won't be reported anymore.
-    $this->fieldInstances = NULL;
   }
 
   /**
diff --git a/src/Entity/SearchApiConfigEntityStorage.php b/src/Entity/SearchApiConfigEntityStorage.php
new file mode 100644
index 00000000..b250affc
--- /dev/null
+++ b/src/Entity/SearchApiConfigEntityStorage.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace Drupal\search_api\Entity;
+
+use Drupal\Core\Config\Entity\ConfigEntityStorage;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\search_api\IndexInterface;
+
+/**
+ * Provides a special storage for Search API config entities.
+ *
+ * This is necessary since post-save hooks would otherwise operate on
+ * override-free entities, which is not desirable in our case.
+ */
+class SearchApiConfigEntityStorage extends ConfigEntityStorage {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function doPostSave(EntityInterface $entity, $update) {
+    $this->resetCache(array($entity->id()));
+
+    // The entity is no longer new.
+    $entity->enforceIsNew(FALSE);
+
+    $overridden_entity = $this->load($entity->id());
+    if (isset($entity->original)) {
+      $overridden_entity->original = $entity->original;
+
+      // In the case of indexes, we also need to clone the fields to allow the
+      // correct detection of renamed field. Conversely, we need to set the new,
+      // rename-free fields on the passed index ($entity) so a subsequent save
+      // won't false detect field renames.
+      if ($entity instanceof IndexInterface) {
+        /** @var \Drupal\search_api\IndexInterface $overridden_entity */
+        $old_fields = $entity->original->getFields();
+        $new_fields = $entity->getFields();
+        $saved_fields = $overridden_entity->getFields();
+//        $cloned_fields = [];
+//        foreach ($saved_fields as $field_id => $field) {
+//          $field = clone $field;
+//          $field->setIndex($entity);
+//          $cloned_fields[$field_id] = $field;
+//        }
+//        $entity->setFields($cloned_fields);
+        foreach ($entity->getFieldRenames() as $old_id => $new_id) {
+          if (!empty($old_fields[$old_id]) && !empty($saved_fields[$new_id])) {
+            $field = clone $new_fields[$new_id];
+            $field->setIndex($overridden_entity);
+            $saved_fields[$new_id] = $field;
+          }
+        }
+        $overridden_entity->setFields($saved_fields);
+      }
+    }
+
+    // Allow code to run after saving.
+    $overridden_entity->postSave($this, $update);
+    $this->invokeHook($update ? 'update' : 'insert', $overridden_entity);
+
+    if ($entity instanceof IndexInterface) {
+      // Reset the field instances so saved renames won't be reported anymore.
+      $entity->discardFieldChanges();
+      $overridden_entity->discardFieldChanges();
+    }
+
+    // After saving, this is now the "original entity", and subsequent saves
+    // will be updates instead of inserts, and updates must always be able to
+    // correctly identify the original entity.
+    $entity->setOriginalId($entity->id());
+    $overridden_entity->setOriginalId($entity->id());
+
+    unset($entity->original);
+    unset($overridden_entity->original);
+  }
+
+}
diff --git a/src/Entity/Server.php b/src/Entity/Server.php
index 08a21c6a..a69335df 100644
--- a/src/Entity/Server.php
+++ b/src/Entity/Server.php
@@ -9,6 +9,7 @@
 use Drupal\search_api\Query\QueryInterface;
 use Drupal\search_api\SearchApiException;
 use Drupal\search_api\ServerInterface;
+use Drupal\search_api\Utility\Utility;
 
 /**
  * Defines the search server configuration entity.
@@ -24,7 +25,7 @@
  *     plural = "@count search servers",
  *   ),
  *   handlers = {
- *     "storage" = "Drupal\Core\Config\Entity\ConfigEntityStorage",
+ *     "storage" = "Drupal\search_api\Entity\SearchApiConfigEntityStorage",
  *     "form" = {
  *       "default" = "Drupal\search_api\Form\ServerForm",
  *       "edit" = "Drupal\search_api\Form\ServerForm",
@@ -465,10 +466,25 @@ public function preSave(EntityStorageInterface $storage) {
       return;
     }
 
+    // Retrieve active config overrides for this server.
+    $overrides = Utility::getConfigOverrides($this);
+
+    if (isset($overrides['backend'])) {
+      $this->backend = $overrides['backend'];
+      $this->backendPlugin = NULL;
+    }
+    if (isset($overrides['backend_config'])) {
+      $this->backend_config = $overrides['backend_config'];
+      $this->backendPlugin = NULL;
+    }
+
     $this->getBackend()->preUpdate();
 
     // If the server is being disabled, also disable all its indexes.
-    if (!$this->isSyncing() && !$this->status() && $this->original->status()) {
+    if (!$this->isSyncing()
+        && !isset($overrides['status'])
+        && !$this->status()
+        && $this->original->status()) {
       foreach ($this->getIndexes(array('status' => TRUE)) as $index) {
         /** @var \Drupal\search_api\IndexInterface $index */
         $index->setStatus(FALSE)->save();
diff --git a/src/IndexInterface.php b/src/IndexInterface.php
index c8f8813b..4b59adeb 100644
--- a/src/IndexInterface.php
+++ b/src/IndexInterface.php
@@ -311,12 +311,15 @@ public function getProcessors();
    * @param string $stage
    *   The stage for which to return the processors. One of the
    *   \Drupal\search_api\Processor\ProcessorInterface::STAGE_* constants.
+   * @param array[] $overrides
+   *   (optional) Overrides to apply to the index's processors, keyed by
+   *   processor IDs with their respective overridden settings as values.
    *
    * @return \Drupal\search_api\Processor\ProcessorInterface[]
    *   An array of all enabled processors that support the given stage, ordered
    *   by the weight for that stage.
    */
-  public function getProcessorsByStage($stage);
+  public function getProcessorsByStage($stage, $overrides = []);
 
   /**
    * Determines whether the given processor ID is valid for this index.
@@ -545,6 +548,13 @@ public function getFulltextFields();
   public function getFieldRenames();
 
   /**
+   * Resets the index's fields to the saved state.
+   *
+   * @return $this
+   */
+  public function discardFieldChanges();
+
+  /**
    * Retrieves the properties of one of this index's datasources.
    *
    * @param string|null $datasource_id
diff --git a/src/UnsavedIndexConfiguration.php b/src/UnsavedIndexConfiguration.php
index 7e7ec7bb..dd7c6b12 100644
--- a/src/UnsavedIndexConfiguration.php
+++ b/src/UnsavedIndexConfiguration.php
@@ -508,6 +508,14 @@ public function getFieldRenames() {
   /**
    * {@inheritdoc}
    */
+  public function discardFieldAndPluginChanges() {
+    $this->discardFieldAndPluginChanges();
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function getPropertyDefinitions($datasource_id) {
     return $this->entity->getPropertyDefinitions($datasource_id);
   }
diff --git a/src/Utility/Utility.php b/src/Utility/Utility.php
index 9ed45bb1..5cd47b81 100644
--- a/src/Utility/Utility.php
+++ b/src/Utility/Utility.php
@@ -2,6 +2,10 @@
 
 namespace Drupal\search_api\Utility;
 
+use Drupal\Component\Utility\NestedArray;
+use Drupal\Core\Config\ConfigFactoryOverrideInterface;
+use Drupal\Core\Config\Entity\ConfigEntityTypeInterface;
+use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\TypedData\ComplexDataDefinitionInterface;
 use Drupal\Core\TypedData\ComplexDataInterface;
 use Drupal\Core\TypedData\DataDefinitionInterface;
@@ -10,6 +14,7 @@
 use Drupal\search_api\IndexInterface;
 use Drupal\search_api\Item\FieldInterface;
 use Drupal\search_api\Plugin\search_api\data_type\value\TextToken;
+use Symfony\Component\DependencyInjection\TaggedContainerInterface;
 
 /**
  * Contains utility methods for the Search API.
@@ -492,4 +497,50 @@ public static function splitPropertyPath($property_path, $separate_last = TRUE,
     return array($property_path, NULL);
   }
 
+  /**
+   * Retrieves all overridden property values for the given config entity.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $entity
+   *   The config entity to check for overrides.
+   *
+   * @return array
+   *   An associative array mapping property names to their overridden values.
+   */
+  public static function getConfigOverrides(EntityInterface $entity) {
+    $entity_type = $entity->getEntityType();
+    if (!($entity_type instanceof ConfigEntityTypeInterface)) {
+      return [];
+    }
+
+    $config_key = $entity_type->getConfigPrefix() . '.' . $entity->id();
+    $overrides = [];
+
+    // Overrides from tagged services.
+    $container = \Drupal::getContainer();
+    if ($container instanceof TaggedContainerInterface) {
+      $tags = $container->findTaggedServiceIds('config.factory.override');
+      foreach (array_keys($tags) as $service_id) {
+        $override = $container->get($service_id);
+        if ($override instanceof ConfigFactoryOverrideInterface) {
+          $service_overrides = $override->loadOverrides([$config_key]);
+          if (!empty($service_overrides[$config_key])) {
+            // Existing overrides take precedence since these will have been
+            // added by events with a higher priority.
+            $arrays = [$service_overrides[$config_key], $overrides];
+            $overrides = NestedArray::mergeDeepArray($arrays, TRUE);
+          }
+        }
+      }
+    }
+
+    // Overrides from settings.php. (This takes precedence over overrides from
+    // services.)
+    if (isset($GLOBALS['config'][$config_key])) {
+      $arrays = [$overrides, $GLOBALS['config'][$config_key]];
+      $overrides = NestedArray::mergeDeepArray($arrays, TRUE);
+    }
+
+    return $overrides;
+  }
+
 }
diff --git a/tests/src/Kernel/BackendTestBase.php b/tests/src/Kernel/BackendTestBase.php
index 73f3175f..5157dc72 100644
--- a/tests/src/Kernel/BackendTestBase.php
+++ b/tests/src/Kernel/BackendTestBase.php
@@ -1018,6 +1018,8 @@ protected function regressionTest2471509() {
 
     $index->getField('body')->setType('text');
     $index->save();
+    $count = $this->indexItems($this->indexId);
+    $this->assertEquals(count($this->entities), $count, 'All items needed to be re-indexed after switching type from string to text.');
   }
 
   /**
diff --git a/tests/src/Kernel/IndexChangesTest.php b/tests/src/Kernel/IndexChangesTest.php
index 1aa64b9b..44a0385a 100644
--- a/tests/src/Kernel/IndexChangesTest.php
+++ b/tests/src/Kernel/IndexChangesTest.php
@@ -266,11 +266,7 @@ public function testTrackerChange() {
     $this->taskManager->executeAllTasks();
 
     $methods = $this->getCalledMethods('tracker');
-    // Note: The initial "trackAllItemsUpdated" call comes from the test
-    // backend, which marks the index for re-indexing every time it gets
-    // updated.
     $expected = array(
-      'trackAllItemsUpdated',
       'trackItemsInserted',
       'trackItemsInserted',
     );