diff --git a/src/pretix/api/urls.py b/src/pretix/api/urls.py
index 6286576187..4bcbd66d5b 100644
--- a/src/pretix/api/urls.py
+++ b/src/pretix/api/urls.py
@@ -41,8 +41,8 @@ from rest_framework import routers
 from pretix.api.views import cart
 
 from .views import (
-    checkin, device, discount, event, exporters, item, oauth, order, organizer,
-    upload, user, version, voucher, waitinglist, webhooks,
+    checkin, device, discount, event, exporters, idempotency, item, oauth,
+    order, organizer, upload, user, version, voucher, waitinglist, webhooks,
 )
 
 router = routers.DefaultRouter()
@@ -133,6 +133,7 @@ urlpatterns = [
     re_path(r"^device/roll$", device.RollKeyView.as_view(), name="device.roll"),
     re_path(r"^device/revoke$", device.RevokeKeyView.as_view(), name="device.revoke"),
     re_path(r"^device/eventselection$", device.EventSelectionView.as_view(), name="device.eventselection"),
+    re_path(r"^idempotency_query$", idempotency.IdempotencyQueryView.as_view(), name="idempotency.query"),
     re_path(r"^upload$", upload.UploadView.as_view(), name="upload"),
     re_path(r"^me$", user.MeView.as_view(), name="user.me"),
     re_path(r"^version$", version.VersionView.as_view(), name="version"),
diff --git a/src/pretix/api/views/idempotency.py b/src/pretix/api/views/idempotency.py
new file mode 100644
index 0000000000..3ae560b01e
--- /dev/null
+++ b/src/pretix/api/views/idempotency.py
@@ -0,0 +1,80 @@
+#
+# This file is part of pretix (Community Edition).
+#
+# Copyright (C) 2014-2020 Raphael Michel and contributors
+# Copyright (C) 2020-2021 rami.io GmbH and contributors
+#
+# This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General
+# Public License as published by the Free Software Foundation in version 3 of the License.
+#
+# ADDITIONAL TERMS APPLY: Pursuant to Section 7 of the GNU Affero General Public License, additional terms are
+# applicable granting you additional permissions and placing additional restrictions on your usage of this software.
+# Please refer to the pretix LICENSE file to obtain the full terms applicable to this work. If you did not receive
+# this file, see <https://pretix.eu/about/en/license>.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
+# <https://www.gnu.org/licenses/>.
+#
+import json
+import logging
+from hashlib import sha1
+
+from django.conf import settings
+from django.http import HttpResponse, JsonResponse
+from rest_framework import status
+from rest_framework.views import APIView
+
+from pretix.api.models import ApiCall
+
+logger = logging.getLogger(__name__)
+
+
+class IdempotencyQueryView(APIView):
+    # Experimental feature, therefore undocumented for now
+    authentication_classes = ()
+    permission_classes = ()
+
+    def get(self, request, format=None):
+        idempotency_key = request.GET.get("key")
+        auth_hash_parts = '{}:{}'.format(
+            request.headers.get('Authorization', ''),
+            request.COOKIES.get(settings.SESSION_COOKIE_NAME, '')
+        )
+        auth_hash = sha1(auth_hash_parts.encode()).hexdigest()
+        if not idempotency_key:
+            return JsonResponse({
+                'detail': 'No idempotency key given.'
+            }, status=status.HTTP_404_NOT_FOUND)
+
+        try:
+            call = ApiCall.objects.get(
+                auth_hash=auth_hash,
+                idempotency_key=idempotency_key,
+            )
+        except ApiCall.DoesNotExist:
+            return JsonResponse({
+                'detail': 'Idempotency key not seen before.'
+            }, status=status.HTTP_404_NOT_FOUND)
+
+        if call.locked:
+            r = JsonResponse(
+                {'detail': 'Concurrent request with idempotency key.'},
+                status=status.HTTP_409_CONFLICT,
+            )
+            r['Retry-After'] = 5
+            return r
+
+        content = call.response_body
+        if isinstance(content, memoryview):
+            content = content.tobytes()
+        r = HttpResponse(
+            content=content,
+            status=call.response_code,
+        )
+        for k, v in json.loads(call.response_headers).values():
+            r[k] = v
+        return r
diff --git a/src/tests/api/test_idempotency.py b/src/tests/api/test_idempotency.py
index c7915523e2..baec6dda30 100644
--- a/src/tests/api/test_idempotency.py
+++ b/src/tests/api/test_idempotency.py
@@ -103,6 +103,19 @@ def test_ignore_path_method_body(token_client, organizer):
     assert resp.status_code == 201
 
 
+@pytest.mark.django_db
+def test_query_key(token_client, organizer):
+    resp = token_client.post('/api/v1/organizers/{}/events/'.format(organizer.slug),
+                             PAYLOAD, format='json', HTTP_X_IDEMPOTENCY_KEY='foo')
+    assert resp.status_code == 201
+    data = resp.content
+    resp = token_client.get('/api/v1/idempotency_query?key=foo')
+    assert resp.content == data
+    assert resp.status_code == 201
+    resp = token_client.get('/api/v1/idempotency_query?key=bar')
+    assert resp.status_code == 404
+
+
 @pytest.mark.django_db
 def test_scoped_by_token(token_client, device, organizer):
     resp = token_client.post('/api/v1/organizers/{}/events/'.format(organizer.slug),