diff --git a/treeherder/webapp/api/internal_issue.py b/treeherder/webapp/api/internal_issue.py
new file mode 100644
index 00000000000..2c19a6bbed9
--- /dev/null
+++ b/treeherder/webapp/api/internal_issue.py
@@ -0,0 +1,57 @@
+from datetime import timedelta
+
+from django.db import transaction
+from django.utils import timezone
+from rest_framework import generics, serializers
+
+from treeherder.model.models import Bugscache, FailureLine
+
+# Only track occurrences of a bug on a specific time window
+BUGSCACHE_OCCURENCES_WINDOW = timedelta(days=7)
+
+
+class InternalIssueSerializer(serializers.Serializer):
+    failure_line_id = serializers.PrimaryKeyRelatedField(
+        write_only=True,
+        source="failure_line",
+        queryset=FailureLine.objects.all(),
+    )
+    occurrences = serializers.SerializerMethodField(read_only=True)
+
+    def get_occurrences(self, bug):
+        return bug.occurrences.filter(created__gte=timezone.now() - BUGSCACHE_OCCURENCES_WINDOW)
+
+    @transaction.atomic
+    def create(self, validated_data):
+        failure_line = validated_data["failure_line"]
+
+        # TODO: Fetch all the similar failure lines
+        similar_failure_lines = [failure_line.id]
+
+        # Build or retrieve a bug already reported for a similar FailureLine
+        bug = Bugscache.objects.filter(occurrences__failure_line__in=similar_failure_lines).first()
+        if bug is None:
+            # TODO: Support writting summary field from the FailureLine information
+            bug = Bugscache.objects.create()
+
+        bug.occurrences.get_or_create(
+            user=self.context["request"].user,
+            failure_line=failure_line,
+            bug=bug,
+        )
+        return bug
+
+    class Meta:
+        model = Bugscache
+        fields = ["failure_line_id", "occurrences"]
+
+
+class CreateInternalIssue(generics.CreateAPIView):
+    """
+    Create a Bugscache entry, not necessarilly linked to a real Bugzilla ticket.
+    In case it already exists, update its occurrences.
+
+    Returns the number of occurrences of this bug in the last week.
+    """
+
+    serializer_class = InternalIssueSerializer
diff --git a/treeherder/webapp/api/urls.py b/treeherder/webapp/api/urls.py
index f9e596c61b1..1172be69435 100644
--- a/treeherder/webapp/api/urls.py
+++ b/treeherder/webapp/api/urls.py
@@ -13,6 +13,7 @@
     groups,
     infra_compare,
     intermittents_view,
+    internal_issue,
     investigated_test,
     job_log_url,
     jobs,
@@ -175,4 +176,7 @@
     ),
     re_path(r"^csp-report/$", csp_report.csp_report_collector, name="csp-report"),
     re_path(r"^schema/", get_schema_view(title="Treeherder Rest API"), name="openapi-schema"),
+    re_path(
+        r"^internal_issue/", internal_issue.CreateInternalIssue.as_view(), name="internal_issue"
+    ),
 ]