diff --git a/openwisp_monitoring/check/tests/test_models.py b/openwisp_monitoring/check/tests/test_models.py
index 64f820ef2..0b44b601d 100644
--- a/openwisp_monitoring/check/tests/test_models.py
+++ b/openwisp_monitoring/check/tests/test_models.py
@@ -4,6 +4,7 @@
 from django.core.exceptions import ValidationError
 from django.test import TransactionTestCase
 from django.utils.timezone import now
+from freezegun import freeze_time
 from swapper import load_model
 
 from ...device.tests import TestDeviceMonitoringMixin
@@ -126,19 +127,17 @@ def test_config_modified_device_problem(self):
         self.assertEqual(Metric.objects.count(), 0)
         self.assertEqual(AlertSettings.objects.count(), 0)
         check = Check.objects.filter(check=self._CONFIG_APPLIED).first()
-        check.perform_check()
+        with freeze_time(now() - timedelta(minutes=10)):
+            check.perform_check()
         self.assertEqual(Metric.objects.count(), 1)
         self.assertEqual(AlertSettings.objects.count(), 1)
+        # Check needs to be run again without mocking time for threshold crossed
+        check.perform_check()
         m = Metric.objects.first()
         self.assertEqual(m.content_object, d)
         self.assertEqual(m.key, 'config_applied')
         dm = d.monitoring
-        # Health status should not change as threshold time not crossed
-        self.assertEqual(dm.status, 'ok')
-        self.assertTrue(m.is_healthy)
-        m.write(0, retention_policy=SHORT_RP, time=now() - timedelta(minutes=10))
         self.assertFalse(m.is_healthy)
-        dm.refresh_from_db()
         self.assertEqual(dm.status, 'problem')
         self.assertEqual(Notification.objects.count(), 1)
 
diff --git a/openwisp_monitoring/db/backends/influxdb/client.py b/openwisp_monitoring/db/backends/influxdb/client.py
index d1ed05119..ddacfe49c 100644
--- a/openwisp_monitoring/db/backends/influxdb/client.py
+++ b/openwisp_monitoring/db/backends/influxdb/client.py
@@ -6,6 +6,7 @@
 
 from django.conf import settings
 from django.core.exceptions import ValidationError
+from django.utils.timezone import now
 from django.utils.functional import cached_property
 from django.utils.translation import gettext_lazy as _
 from influxdb import InfluxDBClient
@@ -112,11 +113,10 @@ def write(self, name, values, **kwargs):
             'tags': kwargs.get('tags'),
             'fields': values,
         }
-        timestamp = kwargs.get('timestamp')
+        timestamp = kwargs.get('timestamp') or now()
         if isinstance(timestamp, datetime):
             timestamp = timestamp.strftime('%Y-%m-%dT%H:%M:%SZ')
-        if timestamp:
-            point['time'] = timestamp
+        point['time'] = timestamp
         self.get_db.write(
             {'points': [point]},
             {
@@ -130,15 +130,13 @@ def read(self, key, fields, tags, **kwargs):
         since = kwargs.get('since')
         order = kwargs.get('order')
         limit = kwargs.get('limit')
-        retention_policy = kwargs.get('retention_policy')
+        rp = kwargs.get('retention_policy')
         if extra_fields and extra_fields != '*':
             fields = ', '.join([fields] + extra_fields)
         elif extra_fields == '*':
             fields = '*'
-        if not retention_policy:
-            q = f'SELECT {fields} FROM {key}'
-        else:
-            q = f'SELECT {fields} FROM {retention_policy}.{key}'
+        from_clause = f'{rp}.{key}' if rp else key
+        q = f'SELECT {fields} FROM {from_clause}'
         conditions = []
         if since:
             conditions.append(f'time >= {since}')