diff --git a/apps/ops/api/job.py b/apps/ops/api/job.py
index 3d1cf255c..0beaff278 100644
--- a/apps/ops/api/job.py
+++ b/apps/ops/api/job.py
@@ -1,4 +1,5 @@
 from django.db.models import Count
+from django.db.transaction import atomic
 from rest_framework.views import APIView
 from django.shortcuts import get_object_or_404
 from rest_framework.response import Response
@@ -66,6 +67,7 @@ class JobExecutionViewSet(OrgBulkModelViewSet):
     model = JobExecution
     search_fields = ('material',)
 
+    @atomic
     def perform_create(self, serializer):
         instance = serializer.save()
         instance.job_version = instance.job.version
diff --git a/apps/ops/models/job.py b/apps/ops/models/job.py
index dd248e83d..529e1adda 100644
--- a/apps/ops/models/job.py
+++ b/apps/ops/models/job.py
@@ -235,6 +235,8 @@ class JobExecution(JMSOrgBaseModel):
 
     @property
     def time_cost(self):
+        if not self.date_start:
+            return 0
         if self.is_finished:
             return (self.date_finished - self.date_start).total_seconds()
         return (timezone.now() - self.date_start).total_seconds()