diff --git a/CHANGELOG.md b/CHANGELOG.md
index c3b9084af..576eeb863 100755
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+* [PR-437](https://github.com/itk-dev/hoeringsportal/pull/437)
+  Cleaned up API and added caching
 * [PR-435](https://github.com/itk-dev/hoeringsportal/pull/435)
   Add usable config values for oidc
   Update OIDC documentation
diff --git a/web/modules/custom/hoeringsportal_data/src/Controller/Api/ApiController.php b/web/modules/custom/hoeringsportal_data/src/Controller/Api/ApiController.php
index 0ac1715b7..a16c212f8 100644
--- a/web/modules/custom/hoeringsportal_data/src/Controller/Api/ApiController.php
+++ b/web/modules/custom/hoeringsportal_data/src/Controller/Api/ApiController.php
@@ -2,11 +2,15 @@
 
 namespace Drupal\hoeringsportal_data\Controller\Api;
 
+use Drupal\Core\Cache\Cache;
+use Drupal\Core\Cache\CacheableJsonResponse;
+use Drupal\Core\Cache\CacheableMetadata;
 use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\hoeringsportal_data\Helper\GeoJsonHelper;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\Serializer\Serializer;
 
 /**
@@ -14,34 +18,15 @@
  */
 abstract class ApiController extends ControllerBase {
 
-  /**
-   * The request stack.
-   *
-   * @var \Symfony\Component\HttpFoundation\RequestStack
-   */
-  protected RequestStack $requestStack;
-
-  /**
-   * Helper.
-   *
-   * @var \Drupal\hoeringsportal_data\Helper\GeoJsonHelper
-   */
-  private GeoJsonHelper $geoJsonHelper;
-
-  /**
-   * The serializer.
-   *
-   * @var \Symfony\Component\Serializer\Serializer
-   */
-  protected Serializer $serializer;
-
   /**
    * Constructor.
    */
-  final public function __construct(RequestStack $requestStack, GeoJsonHelper $geoJsonHelper, Serializer $serializer) {
-    $this->requestStack = $requestStack;
-    $this->geoJsonHelper = $geoJsonHelper;
-    $this->serializer = $serializer;
+  final public function __construct(
+    protected readonly RequestStack $requestStack,
+    protected readonly RouteMatchInterface $routeMatch,
+    protected readonly GeoJsonHelper $geoJsonHelper,
+    protected readonly Serializer $serializer,
+  ) {
   }
 
   /**
@@ -50,6 +35,7 @@ final public function __construct(RequestStack $requestStack, GeoJsonHelper $geo
   public static function create(ContainerInterface $container) {
     return new static(
       $container->get('request_stack'),
+      $container->get('current_route_match'),
       $container->get('hoeringsportal_data.geojson_helper'),
       $container->get('serializer')
     );
@@ -79,13 +65,49 @@ protected function generateUrl($name, $parameters = [], $options = []) {
   /**
    * Create a GeoJSON response.
    */
-  protected function createGeoJsonResponse(array $features, string $type = 'FeatureCollection') {
-    $response = new JsonResponse([
-      'features' => $features,
-      'type' => 'FeatureCollection',
+  protected function createGeoJsonResponse(array $features, string $type = 'FeatureCollection', ?array $cacheContexts = NULL, ?array $cacheTags = NULL): CacheableJsonResponse {
+    $response = new CacheableJsonResponse([
+      'features' => array_values(
+        array_filter(
+          $features,
+          static fn (array $item) => isset($item['geometry'])
+        )
+      ),
+      'type' => $type,
     ]);
     $response->headers->set('content-type', 'application/geo+json');
 
+    if ($cacheContexts || $cacheTags) {
+      // @see https://www.drupal.org/docs/drupal-apis/cache-api/cache-tags#s-what
+      $response->addCacheableDependency(
+        (new CacheableMetadata())
+          // @see https://www.drupal.org/docs/drupal-apis/cache-api/cache-contexts
+          ->setCacheContexts($cacheContexts ?? [])
+          ->setCacheMaxAge(Cache::PERMANENT)
+          ->setCacheTags($cacheTags ?? [])
+      );
+    }
+
+    return $response;
+  }
+
+  /**
+   * Adds rels to response.
+   *
+   * @see https://datatracker.ietf.org/doc/html/rfc8288
+   */
+  protected function addRels(Response $response, int $page, bool $hasNext): Response {
+    $routeName = $this->routeMatch->getRouteName();
+    $rels['self'] = $this->generateUrl($routeName, ['page' => $page]);
+    if ($page > 1) {
+      $rels['prev'] = $this->generateUrl($routeName, ['page' => $page - 1]);
+    }
+    if ($hasNext) {
+      $rels['next'] = $this->generateUrl($routeName, ['page' => $page + 1]);
+    }
+    $links = array_map(static fn (string $rel, string $url) => sprintf('<%s>; rel="%s"', $url, $rel), array_keys($rels), array_values($rels));
+    $response->headers->add(['link' => implode(', ', $links)]);
+
     return $response;
   }
 
diff --git a/web/modules/custom/hoeringsportal_data/src/Controller/Api/GeoJSON/HearingController.php b/web/modules/custom/hoeringsportal_data/src/Controller/Api/GeoJSON/HearingController.php
index e82faef16..8a2b6e844 100644
--- a/web/modules/custom/hoeringsportal_data/src/Controller/Api/GeoJSON/HearingController.php
+++ b/web/modules/custom/hoeringsportal_data/src/Controller/Api/GeoJSON/HearingController.php
@@ -29,11 +29,12 @@ public function index() {
     }
 
     $entities = $this->helper()->getHearings($conditions);
+    $features = array_map($this->helper()->serializeGeoJsonHearing(...), $entities);
 
-    $features = array_values(array_map([$this->helper(), 'serializeGeoJsonHearing'], $entities));
-    $response = $this->createGeoJsonResponse($features, 'FeatureCollection');
-
-    return $response;
+    return $this->createGeoJsonResponse(
+      $features,
+      cacheTags: ['node_list:hearing'],
+    );
   }
 
 }
diff --git a/web/modules/custom/hoeringsportal_data/src/Controller/Api/GeoJSON/PublicMeetingController.php b/web/modules/custom/hoeringsportal_data/src/Controller/Api/GeoJSON/PublicMeetingController.php
index bc080f5ca..2ab5e1a37 100644
--- a/web/modules/custom/hoeringsportal_data/src/Controller/Api/GeoJSON/PublicMeetingController.php
+++ b/web/modules/custom/hoeringsportal_data/src/Controller/Api/GeoJSON/PublicMeetingController.php
@@ -14,9 +14,12 @@ class PublicMeetingController extends ApiController {
    */
   public function dates() {
     $entities = $this->getDates();
-    $features = array_values(array_map([$this->helper(), 'serializeGeoJsonPublicMeetingDate'], $entities));
+    $features = array_map($this->helper()->serializeGeoJsonPublicMeetingDate(...), $entities);
 
-    return $this->createGeoJsonResponse($features);
+    return $this->createGeoJsonResponse(
+      $features,
+      cacheTags: ['node_list:public_meeting'],
+    );
   }
 
   /**
diff --git a/web/modules/custom/hoeringsportal_data/src/Controller/Api/V2/GeoJSON/HearingController.php b/web/modules/custom/hoeringsportal_data/src/Controller/Api/V2/GeoJSON/HearingController.php
index 962d62621..25c864c2d 100644
--- a/web/modules/custom/hoeringsportal_data/src/Controller/Api/V2/GeoJSON/HearingController.php
+++ b/web/modules/custom/hoeringsportal_data/src/Controller/Api/V2/GeoJSON/HearingController.php
@@ -31,24 +31,19 @@ public function index() {
     }
 
     // We get one more entity that actually needed to check if we have a "next" relation.
-    $entities = $this->helper()->getHearings($conditions, ['created' => 'DESC'], $pageSize+1, $pageSize *($page-1));
+    $entities = $this->helper()->getHearings($conditions, ['created' => 'DESC'], $pageSize + 1, $pageSize * ($page - 1));
     $hasNext = count($entities) > $pageSize;
     array_pop($entities);
     $entities = array_slice($entities, 0, $pageSize);
 
-    $features = array_values(array_map([$this->helper(), 'serializeGeoJsonHearing'], $entities));
-    $response = $this->createGeoJsonResponse($features, 'FeatureCollection');
+    $features = array_map($this->helper()->serializeGeoJsonHearing(...), $entities);
+    $response = $this->createGeoJsonResponse(
+      $features,
+      cacheContexts: ['url.query_args:geometry', 'url.query_args:page', 'url.query_args:page_size'],
+      cacheTags: ['node_list:hearing'],
+    );
 
-    // @see https://datatracker.ietf.org/doc/html/rfc8288
-    $rels['self'] = $this->generateUrl('hoeringsportal_data.api_geojson_v2_hearings', ['page' => $page]);
-    if ($page > 1) {
-      $rels['prev'] = $this->generateUrl('hoeringsportal_data.api_geojson_v2_hearings', ['page' => $page-1]);
-    }
-    if ($hasNext) {
-      $rels['next'] = $this->generateUrl('hoeringsportal_data.api_geojson_v2_hearings', ['page' => $page + 1]);
-    }
-    $links = array_map(function ($rel, $url) { return sprintf('<%s>; rel="%s"', $url, $rel); }, array_keys($rels), array_values($rels));
-    $response->headers->add(['link' => implode(', ', $links)]);
+    $this->addRels($response, $page, $hasNext);
 
     return $response;
   }
diff --git a/web/modules/custom/hoeringsportal_data/src/Helper/GeoJsonHelper.php b/web/modules/custom/hoeringsportal_data/src/Helper/GeoJsonHelper.php
index 7ff301cff..3404159b8 100644
--- a/web/modules/custom/hoeringsportal_data/src/Helper/GeoJsonHelper.php
+++ b/web/modules/custom/hoeringsportal_data/src/Helper/GeoJsonHelper.php
@@ -159,8 +159,7 @@ public function serializeGeoJsonHearing(NodeInterface $hearing) {
 
     $geometryType = $this->getGeometryType($hearing);
 
-    $data = [
-      'properties' => [
+    $properties = [
         'hearing_id' => (int) $hearing->id(),
         'hearing_title' => $hearing->getTitle(),
         'hearing_content_state' => $hearing->get('field_content_state')->value,
@@ -189,11 +188,18 @@ public function serializeGeoJsonHearing(NodeInterface $hearing) {
         'hearing_local_plan_ids' => array_map(function ($lokalplan) {
           return (int) $lokalplan->id;
         }, $lokalplaner),
-      ],
     ];
 
+    // Additional properties for Septima widget.
+    $properties['start_date'] = $properties['hearing_start_date'];
+    $properties['end_date'] = $properties['hearing_reply_deadline'];
+
+    $data = [
+      'properties' => $properties,
+      ];
+
     $geometry = $this->getGeometry($hearing);
-    if (NULL !== $geometry) {
+    if (isset($geometry['geometry'])) {
       $data['geometry'] = $geometry['geometry'];
       $data['type'] = 'Feature';
     }
@@ -244,6 +250,10 @@ public function serializeGeoJsonPublicMeetingDate(object $date) {
       'date_spots' => (int) $data->spots,
     ];
 
+    // Additional properties for Septima widget.
+    $properties['start_date'] = $properties['date_time_from'];
+    $properties['end_date'] = $properties['date_time_to'];
+
     if (isset($data->data->coordinates)) {
       $serialized['geometry'] = [
         'type' => 'Point',