diff --git a/judgels-backends/judgels-server-app/src/main/java/judgels/jerahmeel/submission/programming/SubmissionResource.java b/judgels-backends/judgels-server-app/src/main/java/judgels/jerahmeel/submission/programming/SubmissionResource.java
index c41e317b7..cd6c8260d 100644
--- a/judgels-backends/judgels-server-app/src/main/java/judgels/jerahmeel/submission/programming/SubmissionResource.java
+++ b/judgels-backends/judgels-server-app/src/main/java/judgels/jerahmeel/submission/programming/SubmissionResource.java
@@ -10,12 +10,14 @@
 import static judgels.service.ServiceUtils.checkFound;
 
 import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
 import io.dropwizard.hibernate.UnitOfWork;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import javax.inject.Inject;
 import javax.ws.rs.Consumes;
 import javax.ws.rs.DefaultValue;
@@ -287,7 +289,7 @@ public void regradeSubmission(
 
     @POST
     @Path("/regrade")
-    @UnitOfWork
+    @UnitOfWork(transactional = false)
     public void regradeSubmissions(
             @HeaderParam(AUTHORIZATION) AuthHeader authHeader,
             @QueryParam("containerJid") Optional<String> containerJid,
@@ -298,20 +300,24 @@ public void regradeSubmissions(
         String actorJid = actorChecker.check(authHeader);
         checkAllowed(submissionRoleChecker.canManage(actorJid));
 
+        Map<String, ProblemSubmissionConfig> configsMap = new HashMap<>();
+
         for (int pageNumber = 1;; pageNumber++) {
             List<Submission> submissions = submissionStore.getSubmissions(
                     containerJid,
                     byUserJid(username),
                     byProblemJid(containerJid, problemJid, problemAlias),
                     pageNumber,
-                    PAGE_SIZE).getPage();
+                    100).getPage();
 
             if (submissions.isEmpty()) {
                 break;
             }
 
             var problemJids = Lists.transform(submissions, Submission::getProblemJid);
-            Map<String, ProblemSubmissionConfig> configsMap = sandalphonClient.getProgrammingProblemSubmissionConfigs(problemJids);
+            configsMap.putAll(sandalphonClient.getProgrammingProblemSubmissionConfigs(
+                    Sets.difference(Set.copyOf(problemJids), configsMap.keySet())));
+
             submissionRegrader.regradeSubmissions(submissions, configsMap);
         }
     }
diff --git a/judgels-backends/judgels-server-app/src/main/java/judgels/sandalphon/submission/programming/GradingResponseProcessor.java b/judgels-backends/judgels-server-app/src/main/java/judgels/sandalphon/submission/programming/GradingResponseProcessor.java
index ffb54f5be..e0eb12305 100644
--- a/judgels-backends/judgels-server-app/src/main/java/judgels/sandalphon/submission/programming/GradingResponseProcessor.java
+++ b/judgels-backends/judgels-server-app/src/main/java/judgels/sandalphon/submission/programming/GradingResponseProcessor.java
@@ -3,7 +3,6 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import io.dropwizard.hibernate.UnitOfWork;
 import java.io.IOException;
-import java.time.Duration;
 import java.util.Optional;
 import judgels.gabriel.api.GradingResponse;
 import judgels.messaging.MessageClient;
@@ -15,9 +14,6 @@
 public class GradingResponseProcessor {
     private static final Logger LOGGER = LoggerFactory.getLogger(GradingResponseProcessor.class);
 
-    private static final int MAX_RETRIES = 3;
-    private static final Duration DELAY_BETWEEN_RETRIES = Duration.ofSeconds(5);
-
     private final ObjectMapper mapper;
     private final SubmissionStore submissionStore;
     private final MessageClient messageClient;
@@ -45,28 +41,13 @@ public void process(Message message) {
             return;
         }
 
-        boolean gradingExists = false;
-
-        // it is possible that the grading model is not immediately found, because it is not flushed yet.
-        for (int i = 0; i < MAX_RETRIES; i++) {
-            Optional<Submission> submission =
-                    submissionStore.updateGrading(response.getGradingJid(), response.getResult());
-            if (submission.isPresent()) {
-                gradingExists = true;
-                submissionConsumer.accept(submission.get());
-                messageClient.confirmMessage(message.getId());
-                break;
-            }
-
-            try {
-                Thread.sleep(DELAY_BETWEEN_RETRIES.toMillis());
-            } catch (InterruptedException e) {
-                Thread.currentThread().interrupt();
-            }
-        }
-
-        if (!gradingExists) {
+        Optional<Submission> submission = submissionStore.updateGrading(response.getGradingJid(), response.getResult());
+        if (submission.isEmpty()) {
             LOGGER.error("Failed to find grading jid {}", response.getGradingJid());
+            return;
         }
+
+        submissionConsumer.accept(submission.get());
+        messageClient.confirmMessage(message.getId());
     }
 }
diff --git a/judgels-backends/judgels-server-app/src/main/java/judgels/uriel/contest/submission/programming/ContestSubmissionResource.java b/judgels-backends/judgels-server-app/src/main/java/judgels/uriel/contest/submission/programming/ContestSubmissionResource.java
index 5a82fe2b0..53aed1008 100644
--- a/judgels-backends/judgels-server-app/src/main/java/judgels/uriel/contest/submission/programming/ContestSubmissionResource.java
+++ b/judgels-backends/judgels-server-app/src/main/java/judgels/uriel/contest/submission/programming/ContestSubmissionResource.java
@@ -14,9 +14,11 @@
 
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
 import io.dropwizard.hibernate.UnitOfWork;
 import java.util.Collections;
 import java.util.Date;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -318,7 +320,7 @@ public void regradeSubmission(
 
     @POST
     @Path("/regrade")
-    @UnitOfWork
+    @UnitOfWork(transactional = false)
     public void regradeSubmissions(
             @HeaderParam(AUTHORIZATION) AuthHeader authHeader,
             @QueryParam("contestJid") String contestJid,
@@ -331,20 +333,24 @@ public void regradeSubmissions(
 
         Optional<String> problemJid = byProblemJid(contestJid, problemAlias);
 
+        Map<String, ProblemSubmissionConfig> configsMap = new HashMap<>();
+
         for (int pageNumber = 1;; pageNumber++) {
             List<Submission> submissions = submissionStore.getSubmissions(
                     Optional.of(contestJid),
                     byUserJid(username),
                     problemJid,
                     pageNumber,
-                    PAGE_SIZE).getPage();
+                    100).getPage();
 
             if (submissions.isEmpty()) {
                 break;
             }
 
             var problemJids = Lists.transform(submissions, Submission::getProblemJid);
-            Map<String, ProblemSubmissionConfig> configsMap = sandalphonClient.getProgrammingProblemSubmissionConfigs(problemJids);
+            configsMap.putAll(sandalphonClient.getProgrammingProblemSubmissionConfigs(
+                    Sets.difference(Set.copyOf(problemJids), configsMap.keySet())));
+
             submissionRegrader.regradeSubmissions(submissions, configsMap);
         }
         scoreboardIncrementalMarker.invalidateMark(contest.getJid());