diff --git a/src/extension_shield/api/main.py b/src/extension_shield/api/main.py
index 3ebbc4c..bf77ec7 100644
--- a/src/extension_shield/api/main.py
+++ b/src/extension_shield/api/main.py
@@ -6,6 +6,7 @@
 """
 
 import base64
+import hmac
 import mimetypes
 import os
 from pathlib import Path
@@ -469,7 +470,7 @@ def _require_admin_key(request: Request) -> None:
             detail="X-Admin-Key header is required"
         )
     
-    if provided_key != admin_key:
+    if not hmac.compare_digest(str(provided_key), str(admin_key)):
         raise HTTPException(
             status_code=403,
             detail="Invalid admin API key"
@@ -496,7 +497,11 @@ def _require_admin_or_telemetry_key(request: Request) -> None:
             status_code=403,
             detail="X-Admin-Key header is required"
         )
-    valid = (admin_key and provided == admin_key) or (telemetry_key and provided == telemetry_key)
+    valid = (
+        bool(admin_key) and hmac.compare_digest(str(provided), str(admin_key))
+    ) or (
+        bool(telemetry_key) and hmac.compare_digest(str(provided), str(telemetry_key))
+    )
     if not valid:
         raise HTTPException(
             status_code=403,
diff --git a/tests/api/test_admin_endpoints.py b/tests/api/test_admin_endpoints.py
index 4f6f665..2e8c49b 100644
--- a/tests/api/test_admin_endpoints.py
+++ b/tests/api/test_admin_endpoints.py
@@ -128,6 +128,32 @@ def test_delete_scan_with_correct_admin_key_succeeds(self, client, admin_key):
                 # Should succeed (200 or 204 depending on implementation)
                 assert response.status_code in [200, 204, 404]  # 404 if extension not found in DB
 
+    def test_delete_scan_uses_constant_time_key_compare(self, client, admin_key):
+        """DELETE should validate admin key through compare_digest."""
+        with patch("extension_shield.api.main.get_settings") as mock_get_settings, \
+             patch("extension_shield.utils.mode.get_feature_flags") as mock_flags, \
+             patch("extension_shield.api.main.hmac.compare_digest", return_value=False) as mock_compare:
+            from unittest.mock import MagicMock
+            settings = MagicMock()
+            settings.admin_api_key = admin_key
+            settings.telemetry_admin_key = None
+            mock_get_settings.return_value = settings
+            flags = MagicMock()
+            flags.mode = "cloud"
+            flags.telemetry_enabled = True
+            mock_flags.return_value = flags
+
+            test_extension_id = "test-ext-123"
+            scan_results[test_extension_id] = {"extension_id": test_extension_id, "status": "completed"}
+
+            response = client.delete(
+                f"/api/scan/{test_extension_id}",
+                headers={"X-Admin-Key": admin_key},
+            )
+
+            assert response.status_code == 403
+            mock_compare.assert_called_once()
+
     def test_delete_scan_without_configured_admin_key_returns_403(self, client):
         """DELETE when admin key is not configured should return 403."""
         with patch("extension_shield.api.main.get_settings") as mock_get_settings, \
@@ -266,6 +292,38 @@ def test_telemetry_summary_with_telemetry_key_succeeds(self, client, admin_key,
 
                 assert response.status_code == 200
 
+    def test_telemetry_summary_uses_constant_time_key_compare(self, client, admin_key, telemetry_key):
+        """GET should validate admin or telemetry key through compare_digest."""
+        with patch("extension_shield.api.main.get_settings") as mock_get_settings, \
+             patch("extension_shield.utils.mode.get_feature_flags") as mock_flags, \
+             patch("extension_shield.api.main.hmac.compare_digest", side_effect=[False, True]) as mock_compare:
+            from unittest.mock import MagicMock
+            settings = MagicMock()
+            settings.admin_api_key = admin_key
+            settings.telemetry_admin_key = telemetry_key
+            mock_get_settings.return_value = settings
+            flags = MagicMock()
+            flags.mode = "cloud"
+            flags.telemetry_enabled = True
+            mock_flags.return_value = flags
+
+            with patch("extension_shield.api.main.db") as mock_db:
+                mock_db.get_page_view_summary.return_value = {
+                    "days": 14,
+                    "start_day": None,
+                    "end_day": None,
+                    "by_day": {},
+                    "by_path": {},
+                    "rows": [],
+                }
+                response = client.get(
+                    "/api/telemetry/summary",
+                    headers={"X-Admin-Key": telemetry_key},
+                )
+
+                assert response.status_code == 200
+                assert mock_compare.call_count == 2
+
     def test_telemetry_summary_falls_back_to_admin_key(self, client, admin_key):
         """GET should fallback to ADMIN_API_KEY when TELEMETRY_ADMIN_KEY is not set."""
         with patch("extension_shield.api.main.get_settings") as mock_get_settings, \