diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a1915a3767f5..d89f509edbda9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -85,7 +85,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Fix multi-search with template doesn't return status code ([#16265](https://github.com/opensearch-project/OpenSearch/pull/16265))
 - [Streaming Indexing] Fix intermittent 'The bulk request must be terminated by a newline [\n]' failures [#16337](https://github.com/opensearch-project/OpenSearch/pull/16337))
 - Fix wrong default value when setting `index.number_of_routing_shards` to null on index creation ([#16331](https://github.com/opensearch-project/OpenSearch/pull/16331))
-- Fix disk usage exceeds threshold cluster can't spin up issue ([#15258](https://github.com/opensearch-project/OpenSearch/pull/15258)))
+- [Workload Management] Make query groups persistent across process restarts [#16370](https://github.com/opensearch-project/OpenSearch/pull/16370)
 
 - Fix inefficient Stream API call chains ending with count() ([#15386](https://github.com/opensearch-project/OpenSearch/pull/15386))
 
diff --git a/distribution/tools/keystore-cli/src/test/java/org/opensearch/bootstrap/BootstrapTests.java b/distribution/tools/keystore-cli/src/test/java/org/opensearch/bootstrap/BootstrapTests.java
index 7aa63a2736a8c..e9219de218aef 100644
--- a/distribution/tools/keystore-cli/src/test/java/org/opensearch/bootstrap/BootstrapTests.java
+++ b/distribution/tools/keystore-cli/src/test/java/org/opensearch/bootstrap/BootstrapTests.java
@@ -31,7 +31,6 @@
 
 package org.opensearch.bootstrap;
 
-import org.opensearch.common.logging.LogConfigurator;
 import org.opensearch.common.settings.KeyStoreCommandTestCase;
 import org.opensearch.common.settings.KeyStoreWrapper;
 import org.opensearch.common.settings.SecureSettings;
@@ -39,7 +38,6 @@
 import org.opensearch.common.util.io.IOUtils;
 import org.opensearch.core.common.settings.SecureString;
 import org.opensearch.env.Environment;
-import org.opensearch.node.Node;
 import org.opensearch.test.OpenSearchTestCase;
 import org.junit.After;
 import org.junit.Before;
@@ -53,14 +51,8 @@
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.concurrent.CountDownLatch;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.hamcrest.Matchers.equalTo;
-import static org.mockito.Mockito.doAnswer;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.verify;
 
 public class BootstrapTests extends OpenSearchTestCase {
     Environment env;
@@ -139,38 +131,4 @@ private void assertPassphraseRead(String source, String expected) {
         }
     }
 
-    public void testInitExecutionOrder() throws Exception {
-        AtomicInteger order = new AtomicInteger(0);
-        CountDownLatch countDownLatch = new CountDownLatch(1);
-        Thread mockThread = new Thread(() -> {
-            assertEquals(0, order.getAndIncrement());
-            countDownLatch.countDown();
-        });
-
-        Node mockNode = mock(Node.class);
-        doAnswer(invocation -> {
-            try {
-                boolean threadStarted = countDownLatch.await(1000, TimeUnit.MILLISECONDS);
-                assertTrue(
-                    "Waited for one second but the keepAliveThread isn't started, please check the execution order of"
-                        + "keepAliveThread.start and node.start",
-                    threadStarted
-                );
-            } catch (InterruptedException e) {
-                fail("Thread interrupted");
-            }
-            assertEquals(1, order.getAndIncrement());
-            return null;
-        }).when(mockNode).start();
-
-        LogConfigurator.registerErrorListener();
-        Bootstrap testBootstrap = new Bootstrap(mockThread, mockNode);
-        Bootstrap.setInstance(testBootstrap);
-
-        Bootstrap.startInstance(testBootstrap);
-
-        verify(mockNode).start();
-        assertEquals(2, order.get());
-    }
-
 }
diff --git a/libs/core/src/main/java/org/opensearch/core/common/io/stream/Writeable.java b/libs/core/src/main/java/org/opensearch/core/common/io/stream/Writeable.java
index 960f4bec5eeb5..a46f2bebe3ad2 100644
--- a/libs/core/src/main/java/org/opensearch/core/common/io/stream/Writeable.java
+++ b/libs/core/src/main/java/org/opensearch/core/common/io/stream/Writeable.java
@@ -83,7 +83,7 @@ public static <R extends Reader<?>> void registerReader(final byte ordinal, fina
 
         public static void registerClassAlias(final Class<?> classInstance, final Class<?> classGeneric) {
             if (WRITER_CUSTOM_CLASS_MAP.putIfAbsent(classInstance, classGeneric) != null) {
-                throw new IllegalArgumentException("Streamable custom class already registered [" + classInstance.getClass() + "]");
+                throw new IllegalArgumentException("Streamable custom class already registered [" + classInstance.getName() + "]");
             }
         }
 
@@ -96,7 +96,7 @@ public static <W extends Writer<?>> W getWriter(final Class<?> clazz) {
         }
 
         /**
-         * Returns the ristered reader keyed by the unique ordinal
+         * Returns the registered reader keyed by the unique ordinal
          */
         @SuppressWarnings("unchecked")
         public static <R extends Reader<?>> R getReader(final byte b) {
diff --git a/libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java b/libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java
index bbb55204712d1..82cc3951be753 100644
--- a/libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java
+++ b/libs/core/src/main/java/org/opensearch/core/xcontent/MediaTypeRegistry.java
@@ -57,6 +57,7 @@
 public final class MediaTypeRegistry {
     private static Map<String, MediaType> formatToMediaType = Map.of();
     private static Map<String, MediaType> typeWithSubtypeToMediaType = Map.of();
+    private static Map<String, MediaType> knownStringsToMediaType = Map.of();
 
     // Default mediaType singleton
     private static MediaType DEFAULT_MEDIA_TYPE;
@@ -84,6 +85,8 @@ private static void register(MediaType[] acceptedMediaTypes, Map<String, MediaTy
         // ensures the map is not overwritten:
         Map<String, MediaType> typeMap = new HashMap<>(typeWithSubtypeToMediaType);
         Map<String, MediaType> formatMap = new HashMap<>(formatToMediaType);
+        Map<String, MediaType> knownStringMap = new HashMap<>(knownStringsToMediaType);
+
         for (MediaType mediaType : acceptedMediaTypes) {
             if (formatMap.containsKey(mediaType.format())) {
                 throw new IllegalArgumentException("unable to register mediaType: [" + mediaType.format() + "]. Type already exists.");
@@ -107,13 +110,24 @@ private static void register(MediaType[] acceptedMediaTypes, Map<String, MediaTy
             MediaType mediaType = entry.getValue();
             typeMap.put(typeWithSubtype, mediaType);
             formatMap.putIfAbsent(mediaType.format(), mediaType); // ignore if the additional type mapping already exists
+            knownStringMap.put(mediaType.mediaType(), mediaType);
+            knownStringMap.put(mediaType.mediaTypeWithoutParameters(), mediaType);
         }
 
         formatToMediaType = Map.copyOf(formatMap);
         typeWithSubtypeToMediaType = Map.copyOf(typeMap);
+        knownStringsToMediaType = Map.copyOf(knownStringMap);
     }
 
     public static MediaType fromMediaType(String mediaType) {
+        if (mediaType == null) {
+            return null;
+        }
+        // Skip parsing if the string is an exact match for any known string value
+        final MediaType knownMediaType = knownStringsToMediaType.get(mediaType);
+        if (knownMediaType != null) {
+            return knownMediaType;
+        }
         ParsedMediaType parsedMediaType = parseMediaType(mediaType);
         return parsedMediaType != null ? parsedMediaType.getMediaType() : null;
     }
diff --git a/libs/core/src/test/java/org/opensearch/core/common/io/stream/WriteableTests.java b/libs/core/src/test/java/org/opensearch/core/common/io/stream/WriteableTests.java
new file mode 100644
index 0000000000000..60ba0b2111f80
--- /dev/null
+++ b/libs/core/src/test/java/org/opensearch/core/common/io/stream/WriteableTests.java
@@ -0,0 +1,30 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.core.common.io.stream;
+
+import org.opensearch.test.OpenSearchTestCase;
+import org.junit.Assert;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class WriteableTests extends OpenSearchTestCase {
+
+    public void testRegisterClassAlias() {
+        Writeable.WriteableRegistry.registerClassAlias(StringBuilder.class, AtomicInteger.class);
+        try {
+            Writeable.WriteableRegistry.registerClassAlias(StringBuilder.class, AtomicInteger.class);
+            Assert.fail("expected exception not thrown");
+        } catch (IllegalArgumentException illegalArgumentException) {
+            Assert.assertEquals(
+                "Streamable custom class already registered [java.lang.StringBuilder]",
+                illegalArgumentException.getMessage()
+            );
+        }
+    }
+}
diff --git a/server/src/main/java/org/opensearch/bootstrap/Bootstrap.java b/server/src/main/java/org/opensearch/bootstrap/Bootstrap.java
index 757e2c9da6e49..4e167d10b99fa 100644
--- a/server/src/main/java/org/opensearch/bootstrap/Bootstrap.java
+++ b/server/src/main/java/org/opensearch/bootstrap/Bootstrap.java
@@ -93,17 +93,6 @@ final class Bootstrap {
     private final Thread keepAliveThread;
     private final Spawner spawner = new Spawner();
 
-    // For testing purpose
-    static void setInstance(Bootstrap bootstrap) {
-        INSTANCE = bootstrap;
-    }
-
-    // For testing purpose
-    Bootstrap(Thread keepAliveThread, Node node) {
-        this.keepAliveThread = keepAliveThread;
-        this.node = node;
-    }
-
     /** creates a new instance */
     Bootstrap() {
         keepAliveThread = new Thread(new Runnable() {
@@ -347,10 +336,8 @@ private static Environment createEnvironment(
     }
 
     private void start() throws NodeValidationException {
-        // keepAliveThread should start first than node to ensure the cluster can spin up successfully in edge cases:
-        // https://github.com/opensearch-project/OpenSearch/issues/14791
-        keepAliveThread.start();
         node.start();
+        keepAliveThread.start();
     }
 
     static void stop() throws IOException {
@@ -423,7 +410,7 @@ static void init(final boolean foreground, final Path pidFile, final boolean qui
                 throw new BootstrapException(e);
             }
 
-            startInstance(INSTANCE);
+            INSTANCE.start();
 
             // We don't close stderr if `--quiet` is passed, because that
             // hides fatal startup errors. For example, if OpenSearch is
@@ -475,10 +462,6 @@ static void init(final boolean foreground, final Path pidFile, final boolean qui
         }
     }
 
-    static void startInstance(Bootstrap instance) throws NodeValidationException {
-        instance.start();
-    }
-
     @SuppressForbidden(reason = "System#out")
     private static void closeSystOut() {
         System.out.close();
diff --git a/server/src/main/java/org/opensearch/cluster/ClusterModule.java b/server/src/main/java/org/opensearch/cluster/ClusterModule.java
index 66b1740c8fa96..9081432093106 100644
--- a/server/src/main/java/org/opensearch/cluster/ClusterModule.java
+++ b/server/src/main/java/org/opensearch/cluster/ClusterModule.java
@@ -327,6 +327,13 @@ public static List<NamedXContentRegistry.Entry> getNamedXWriteables() {
                 DecommissionAttributeMetadata::fromXContent
             )
         );
+        entries.add(
+            new NamedXContentRegistry.Entry(
+                Metadata.Custom.class,
+                new ParseField(QueryGroupMetadata.TYPE),
+                QueryGroupMetadata::fromXContent
+            )
+        );
         return entries;
     }
 
diff --git a/server/src/main/java/org/opensearch/repositories/RepositoriesService.java b/server/src/main/java/org/opensearch/repositories/RepositoriesService.java
index 7da52147661dc..9aec81536dbd0 100644
--- a/server/src/main/java/org/opensearch/repositories/RepositoriesService.java
+++ b/server/src/main/java/org/opensearch/repositories/RepositoriesService.java
@@ -81,6 +81,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -729,7 +730,7 @@ public static void validateRepositoryMetadataSettings(
                         + " in the name as this delimiter is used to create pinning entity"
                 );
             }
-            if (repositoryWithShallowV2Exists(repositories)) {
+            if (repositoryWithShallowV2Exists(repositories, repositoryName)) {
                 throw new RepositoryException(
                     repositoryName,
                     "setting "
@@ -763,8 +764,13 @@ public static void validateRepositoryMetadataSettings(
         }
     }
 
-    private static boolean repositoryWithShallowV2Exists(Map<String, Repository> repositories) {
-        return repositories.values().stream().anyMatch(repo -> SHALLOW_SNAPSHOT_V2.get(repo.getMetadata().settings()));
+    private static boolean repositoryWithShallowV2Exists(Map<String, Repository> repositories, String repositoryName) {
+        return repositories.values()
+            .stream()
+            .anyMatch(
+                repository -> SHALLOW_SNAPSHOT_V2.get(repository.getMetadata().settings())
+                    && !Objects.equals(repository.getMetadata().name(), repositoryName)
+            );
     }
 
     private static boolean pinnedTimestampExistsWithDifferentRepository(
diff --git a/server/src/main/java/org/opensearch/search/SearchService.java b/server/src/main/java/org/opensearch/search/SearchService.java
index 40afdbfbdaa9e..c2f8b17fcf166 100644
--- a/server/src/main/java/org/opensearch/search/SearchService.java
+++ b/server/src/main/java/org/opensearch/search/SearchService.java
@@ -721,14 +721,15 @@ private SearchPhaseResult executeQueryPhase(ShardSearchRequest request, SearchSh
             }
         } catch (Exception e) {
             // execution exception can happen while loading the cache, strip it
-            if (e instanceof ExecutionException) {
-                e = (e.getCause() == null || e.getCause() instanceof Exception)
-                    ? (Exception) e.getCause()
-                    : new OpenSearchException(e.getCause());
+            Exception exception = e;
+            if (exception instanceof ExecutionException) {
+                exception = (exception.getCause() == null || exception.getCause() instanceof Exception)
+                    ? (Exception) exception.getCause()
+                    : new OpenSearchException(exception.getCause());
             }
-            logger.trace("Query phase failed", e);
-            processFailure(readerContext, e);
-            throw e;
+            logger.trace("Query phase failed", exception);
+            processFailure(readerContext, exception);
+            throw exception;
         } finally {
             taskResourceTrackingService.writeTaskResourceUsage(task, clusterService.localNode().getId());
         }
diff --git a/server/src/test/java/org/opensearch/cluster/ClusterModuleTests.java b/server/src/test/java/org/opensearch/cluster/ClusterModuleTests.java
index f8240e775cfa5..8d2f2b743af9f 100644
--- a/server/src/test/java/org/opensearch/cluster/ClusterModuleTests.java
+++ b/server/src/test/java/org/opensearch/cluster/ClusterModuleTests.java
@@ -71,6 +71,7 @@
 import org.opensearch.common.settings.SettingsModule;
 import org.opensearch.common.util.concurrent.ThreadContext;
 import org.opensearch.core.common.io.stream.NamedWriteableRegistry;
+import org.opensearch.core.xcontent.NamedXContentRegistry;
 import org.opensearch.gateway.GatewayAllocator;
 import org.opensearch.plugins.ClusterPlugin;
 import org.opensearch.telemetry.metrics.noop.NoopMetricsRegistry;
@@ -331,10 +332,18 @@ public void testRejectsDuplicateExistingShardsAllocatorName() {
 
     public void testQueryGroupMetadataRegister() {
         List<NamedWriteableRegistry.Entry> customEntries = ClusterModule.getNamedWriteables();
+        List<NamedXContentRegistry.Entry> customXEntries = ClusterModule.getNamedXWriteables();
         assertTrue(
             customEntries.stream()
                 .anyMatch(entry -> entry.categoryClass == Metadata.Custom.class && entry.name.equals(QueryGroupMetadata.TYPE))
         );
+
+        assertTrue(
+            customXEntries.stream()
+                .anyMatch(
+                    entry -> entry.categoryClass == Metadata.Custom.class && entry.name.getPreferredName().equals(QueryGroupMetadata.TYPE)
+                )
+        );
     }
 
     public void testRerouteServiceSetForBalancedShardsAllocator() {
diff --git a/server/src/test/java/org/opensearch/repositories/blobstore/BlobStoreRepositoryRemoteIndexTests.java b/server/src/test/java/org/opensearch/repositories/blobstore/BlobStoreRepositoryRemoteIndexTests.java
index e280ab8c7a73c..f2b06b0926b81 100644
--- a/server/src/test/java/org/opensearch/repositories/blobstore/BlobStoreRepositoryRemoteIndexTests.java
+++ b/server/src/test/java/org/opensearch/repositories/blobstore/BlobStoreRepositoryRemoteIndexTests.java
@@ -431,6 +431,13 @@ public void testRepositoryCreationShallowV2() throws Exception {
             );
         }
 
+        // Modify repo-1 settings. This should go through
+        updateRepository(
+            client,
+            "test-repo-1",
+            Settings.builder().put(snapshotRepoSettings1).put("max_snapshot_bytes_per_sec", "10k").build()
+        );
+
         // Disable shallow snapshot V2 setting on test-repo-1
         updateRepository(
             client,