diff --git a/webapp/models/source.py b/webapp/models/source.py
index 9907409b..5c7f33c1 100644
--- a/webapp/models/source.py
+++ b/webapp/models/source.py
@@ -79,4 +79,4 @@ def combined_updated_at(self) -> datetime:
             return self.realtime_data_updated_at
         if self.static_data_updated_at:
             return self.static_data_updated_at
-        return self.modified_at
+        return self.modified
diff --git a/webapp/prometheus_api/prometheus_handler.py b/webapp/prometheus_api/prometheus_handler.py
index 37cb0565..345ce1cd 100644
--- a/webapp/prometheus_api/prometheus_handler.py
+++ b/webapp/prometheus_api/prometheus_handler.py
@@ -43,6 +43,11 @@ def __init__(
     def get_metrics(self) -> str:
         sources = self.source_repository.fetch_sources()
 
+        last_modified_metrics = Metrics(
+            help='Last modification in seconds from now',
+            type=MetricType.gauge,
+            identifier='app_ocpdb_source_last_modified',
+        )
         last_static_update_metrics = Metrics(
             help='Last static update in seconds from now',
             type=MetricType.gauge,
@@ -77,6 +82,13 @@ def get_metrics(self) -> str:
             if source.static_status in [SourceStatus.DISABLED, SourceStatus.PROVISIONED]:
                 continue
 
+            last_modified_metrics.metrics.append(
+                SourceMetric(
+                    source=source.uid,
+                    value=int((datetime.now(tz=timezone.utc) - source.modified).total_seconds()),
+                )
+            )
+
             if source.static_data_updated_at:
                 last_static_update_metrics.metrics.append(
                     SourceMetric(
@@ -121,7 +133,8 @@ def get_metrics(self) -> str:
             )
 
         metrics = (
-            failed_static_sources.to_metrics()
+            last_modified_metrics.to_metrics()
+            + failed_static_sources.to_metrics()
             + last_static_update_metrics.to_metrics()
             + source_static_errors.to_metrics()
             + failed_realtime_sources.to_metrics()
diff --git a/webapp/repositories/evse_repository.py b/webapp/repositories/evse_repository.py
index 924e5c2f..69caf7c8 100644
--- a/webapp/repositories/evse_repository.py
+++ b/webapp/repositories/evse_repository.py
@@ -159,7 +159,12 @@ def fetch_evses_by_source_and_uids(self, source_uid: str, uids: list[str]) -> li
         query = (
             self.session
             .query(Evse)
-            .options(selectinload(Evse.connectors))
+            .options(
+                selectinload(Evse.connectors),
+                # save_evse_updates() lifts the EVSE last_updated to its location, so eager-load the whole chain:
+                # with a lot of realtime updates per second, a lazy load per EVSE would be an N+1 on every heartbeat.
+                joinedload(Evse.charging_station).joinedload(ChargingStation.location),
+            )
             .filter(Evse.uid.in_(uids))
             .join(Evse.charging_station)
             .join(ChargingStation.location)
diff --git a/webapp/services/import_services/base_import_service.py b/webapp/services/import_services/base_import_service.py
index afe72ab9..6f2cfd9b 100644
--- a/webapp/services/import_services/base_import_service.py
+++ b/webapp/services/import_services/base_import_service.py
@@ -128,6 +128,14 @@ def save_evse_updates(self, evse_updates: list[EvseUpdate | EvseRealtimeUpdate])
                     continue
                 setattr(evse, key, value)
 
+            # Charging station and location are only as fresh as their freshest EVSE, so lift the new timestamp up
+            # the chain if it is newer.
+            charging_station = evse.charging_station
+            if evse.last_updated > charging_station.last_updated:
+                charging_station.last_updated = evse.last_updated
+            if charging_station.last_updated > charging_station.location.last_updated:
+                charging_station.location.last_updated = charging_station.last_updated
+
             self.evse_repository.save_evse(evse, commit=False)
 
         self.evse_repository.session.commit()
@@ -255,6 +263,12 @@ def save_location_update(
             )
         location.charging_pool = new_charging_stations
 
+        # get_charging_station() already lifted every charging station to its freshest EVSE, so taking the maximum
+        # over the charging stations propagates the newest EVSE timestamp up to the location.
+        for charging_station in new_charging_stations:
+            if charging_station.last_updated > location.last_updated:
+                location.last_updated = charging_station.last_updated
+
         # Fetch official regional code if not set, if all required fields are available and if country is supported
         if (
             not location.official_region_code
@@ -340,6 +354,12 @@ def get_charging_station(
 
         charging_station.evses = new_evses
 
+        # Same rule as in save_evse_updates(): a charging station is only as fresh as its freshest EVSE. Sources
+        # regularly send EVSE timestamps which are newer than the charging station timestamp.
+        for evse in new_evses:
+            if evse.last_updated > charging_station.last_updated:
+                charging_station.last_updated = evse.last_updated
+
         return charging_station
 
     def get_evse(