diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cfadd0edd6..b8cbcf8d67 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -22,7 +22,7 @@ jobs:
       uses: actions/setup-java@v4
       with:
         distribution: temurin # Temurin is a distribution of adoptium
-        java-version: 17
+        java-version: 21
 
     - name: Checkout security
       uses: actions/checkout@v4
@@ -40,7 +40,7 @@ jobs:
       matrix:
         gradle_task: ${{ fromJson(needs.generate-test-list.outputs.separateTestsNames) }}
         platform: [windows-latest, ubuntu-latest]
-        jdk: [11, 17, 21]
+        jdk: [21]
     runs-on: ${{ matrix.platform }}
 
     steps:
@@ -97,7 +97,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        jdk: [11, 17, 21]
+        jdk: [21]
         platform: [ubuntu-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
 
@@ -132,7 +132,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        jdk: [17]
+        jdk: [21]
         platform: [ubuntu-latest]
     runs-on: ${{ matrix.platform }}
 
@@ -159,7 +159,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: temurin # Temurin is a distribution of adoptium
-          java-version: 17
+          java-version: 21
 
       - name: Checkout Security Repo
         uses: actions/checkout@v4
@@ -204,7 +204,7 @@ jobs:
     - uses: actions/setup-java@v4
       with:
         distribution: temurin # Temurin is a distribution of adoptium
-        java-version: 11
+        java-version: 21
     - uses: github/codeql-action/init@v3
       with:
         languages: java
@@ -219,7 +219,7 @@ jobs:
     - uses: actions/setup-java@v4
       with:
         distribution: temurin # Temurin is a distribution of adoptium
-        java-version: 11
+        java-version: 21
 
     - run: |
         security_plugin_version=$(./gradlew properties -q | grep -E '^version:' | awk '{print $2}')
diff --git a/.github/workflows/code-hygiene.yml b/.github/workflows/code-hygiene.yml
index 2f8820709a..bf830e993b 100644
--- a/.github/workflows/code-hygiene.yml
+++ b/.github/workflows/code-hygiene.yml
@@ -22,7 +22,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: temurin # Temurin is a distribution of adoptium
-          java-version: 17
+          java-version: 21
 
       - uses: gradle/gradle-build-action@v3
         with:
@@ -38,7 +38,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: temurin # Temurin is a distribution of adoptium
-          java-version: 11
+          java-version: 21
 
       - uses: gradle/gradle-build-action@v3
         with:
@@ -54,7 +54,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: temurin # Temurin is a distribution of adoptium
-          java-version: 11
+          java-version: 21
 
       - uses: gradle/gradle-build-action@v3
         with:
diff --git a/.github/workflows/integration-tests.yml b/.github/workflows/integration-tests.yml
index 183276e675..cf3904c8cc 100644
--- a/.github/workflows/integration-tests.yml
+++ b/.github/workflows/integration-tests.yml
@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        jdk: [11, 17, 21]
+        jdk: [21]
         test-run: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 
     steps:
diff --git a/.github/workflows/maven-publish.yml b/.github/workflows/maven-publish.yml
index a837289795..d10fd67beb 100644
--- a/.github/workflows/maven-publish.yml
+++ b/.github/workflows/maven-publish.yml
@@ -20,7 +20,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: temurin # Temurin is a distribution of adoptium
-          java-version: 11
+          java-version: 21
       - uses: actions/checkout@v4
       - uses: aws-actions/configure-aws-credentials@v4
         with:
diff --git a/.github/workflows/plugin_install.yml b/.github/workflows/plugin_install.yml
index 8cfcd156ae..12a9edcf60 100644
--- a/.github/workflows/plugin_install.yml
+++ b/.github/workflows/plugin_install.yml
@@ -12,7 +12,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest]
-        jdk: [11, 17, 21]
+        jdk: [21]
     runs-on: ${{ matrix.os }}
 
     steps:
@@ -40,12 +40,13 @@ jobs:
         shell: bash
 
       - name: Run Opensearch with A Single Plugin
-        uses: derek-ho/start-opensearch@v4
+        uses: derek-ho/start-opensearch@main
         with:
           opensearch-version: ${{ env.OPENSEARCH_VERSION }}
           plugins: "file:$(pwd)/${{ env.PLUGIN_NAME }}.zip"
           security-enabled: true
           admin-password: ${{ steps.random-password.outputs.generated_name }}
+          jdk-version: 21
 
       - name: Run sanity tests
         uses: gradle/gradle-build-action@v3
diff --git a/build.gradle b/build.gradle
index 692f23cf77..d495bf291c 100644
--- a/build.gradle
+++ b/build.gradle
@@ -94,8 +94,8 @@ spotbugsTest {
     enabled = false
 }
 
-java.sourceCompatibility = JavaVersion.VERSION_11
-java.targetCompatibility = JavaVersion.VERSION_11
+java.sourceCompatibility = JavaVersion.VERSION_21
+java.targetCompatibility = JavaVersion.VERSION_21
 
 
 compileJava {
diff --git a/src/main/java/com/amazon/dlic/auth/http/jwt/HTTPJwtAuthenticator.java b/src/main/java/com/amazon/dlic/auth/http/jwt/HTTPJwtAuthenticator.java
index 4a863c7cb1..08eaeed65e 100644
--- a/src/main/java/com/amazon/dlic/auth/http/jwt/HTTPJwtAuthenticator.java
+++ b/src/main/java/com/amazon/dlic/auth/http/jwt/HTTPJwtAuthenticator.java
@@ -63,6 +63,7 @@ public class HTTPJwtAuthenticator implements HTTPAuthenticator {
     private final List<String> requiredAudience;
     private final String requireIssuer;
 
+    @SuppressWarnings("removal")
     public HTTPJwtAuthenticator(final Settings settings, final Path configPath) {
         super();
 
diff --git a/src/main/java/com/amazon/dlic/auth/http/kerberos/HTTPSpnegoAuthenticator.java b/src/main/java/com/amazon/dlic/auth/http/kerberos/HTTPSpnegoAuthenticator.java
index 125bbed073..53d60b7261 100644
--- a/src/main/java/com/amazon/dlic/auth/http/kerberos/HTTPSpnegoAuthenticator.java
+++ b/src/main/java/com/amazon/dlic/auth/http/kerberos/HTTPSpnegoAuthenticator.java
@@ -190,6 +190,7 @@ public AuthCredentials run() {
         return creds;
     }
 
+    @SuppressWarnings("removal")
     private AuthCredentials extractCredentials0(final SecurityRequest request) {
 
         if (acceptorPrincipal == null || acceptorKeyTabPath == null) {
diff --git a/src/main/java/org/opensearch/security/DefaultObjectMapper.java b/src/main/java/org/opensearch/security/DefaultObjectMapper.java
index 2d18667c54..d7ec09f5d9 100644
--- a/src/main/java/org/opensearch/security/DefaultObjectMapper.java
+++ b/src/main/java/org/opensearch/security/DefaultObjectMapper.java
@@ -139,6 +139,7 @@ public static <T> T getOrDefault(Map<String, Object> properties, String key, T d
         return value != null ? value : defaultValue;
     }
 
+    @SuppressWarnings("removal")
     public static <T> T readTree(JsonNode node, Class<T> clazz) throws IOException {
 
         final SecurityManager sm = System.getSecurityManager();
diff --git a/src/main/java/org/opensearch/security/configuration/ConfigurationRepository.java b/src/main/java/org/opensearch/security/configuration/ConfigurationRepository.java
index 44ba77428f..d7c5fcaed4 100644
--- a/src/main/java/org/opensearch/security/configuration/ConfigurationRepository.java
+++ b/src/main/java/org/opensearch/security/configuration/ConfigurationRepository.java
@@ -655,6 +655,7 @@ public static int getDefaultConfigVersion() {
         return ConfigurationRepository.DEFAULT_CONFIG_VERSION;
     }
 
+    @SuppressWarnings("removal")
     private class AccessControllerWrappedThread extends Thread {
         private final Thread innerThread;
 
diff --git a/src/main/java/org/opensearch/security/dlic/rest/api/ConfigUpgradeApiAction.java b/src/main/java/org/opensearch/security/dlic/rest/api/ConfigUpgradeApiAction.java
index f295ab8c1c..8559ab49d7 100644
--- a/src/main/java/org/opensearch/security/dlic/rest/api/ConfigUpgradeApiAction.java
+++ b/src/main/java/org/opensearch/security/dlic/rest/api/ConfigUpgradeApiAction.java
@@ -265,6 +265,7 @@ private <T> SecurityDynamicConfiguration<T> loadYamlFile(final String filepath,
         return ConfigHelper.fromYamlFile(filepath, cType, ConfigurationRepository.DEFAULT_CONFIG_VERSION, 0, 0);
     }
 
+    @SuppressWarnings("removal")
     JsonNode loadConfigFileAsJson(final CType cType) throws IOException {
         final var cd = securityApiDependencies.configurationRepository().getConfigDirectory();
         final var filepath = cType.configFile(Path.of(cd)).toString();
diff --git a/src/main/java/org/opensearch/security/hasher/BCryptPasswordHasher.java b/src/main/java/org/opensearch/security/hasher/BCryptPasswordHasher.java
index 043c0392d9..7373fe6f77 100644
--- a/src/main/java/org/opensearch/security/hasher/BCryptPasswordHasher.java
+++ b/src/main/java/org/opensearch/security/hasher/BCryptPasswordHasher.java
@@ -30,6 +30,7 @@ public class BCryptPasswordHasher implements PasswordHasher {
 
     private static final HashingFunction DEFAULT_BCRYPT_FUNCTION = BcryptFunction.getInstance(Bcrypt.Y, 12);
 
+    @SuppressWarnings("removal")
     @Override
     public String hash(char[] password) {
         if (password == null || password.length == 0) {
@@ -49,6 +50,7 @@ public String hash(char[] password) {
         }
     }
 
+    @SuppressWarnings("removal")
     @Override
     public boolean check(char[] password, String hash) {
         if (password == null || password.length == 0) {
diff --git a/src/main/java/org/opensearch/security/http/OnBehalfOfAuthenticator.java b/src/main/java/org/opensearch/security/http/OnBehalfOfAuthenticator.java
index 23db7accda..327a25f849 100644
--- a/src/main/java/org/opensearch/security/http/OnBehalfOfAuthenticator.java
+++ b/src/main/java/org/opensearch/security/http/OnBehalfOfAuthenticator.java
@@ -66,6 +66,7 @@ public class OnBehalfOfAuthenticator implements HTTPAuthenticator {
 
     private final EncryptionDecryptionUtil encryptionUtil;
 
+    @SuppressWarnings("removal")
     public OnBehalfOfAuthenticator(Settings settings, String clusterName) {
         String oboEnabledSetting = settings.get("enabled", "true");
         oboEnabled = Boolean.parseBoolean(oboEnabledSetting);
diff --git a/src/main/java/org/opensearch/security/securityconf/DynamicConfigModelV7.java b/src/main/java/org/opensearch/security/securityconf/DynamicConfigModelV7.java
index ca237bc054..4bc9e82882 100644
--- a/src/main/java/org/opensearch/security/securityconf/DynamicConfigModelV7.java
+++ b/src/main/java/org/opensearch/security/securityconf/DynamicConfigModelV7.java
@@ -425,6 +425,7 @@ private void destroyDestroyables(List<Destroyable> destroyableComponents) {
         }
     }
 
+    @SuppressWarnings("removal")
     private <T> T newInstance(final String clazzOrShortcut, String type, final Settings settings, final Path configPath) {
         final String clazz = authImplMap.computeIfAbsent(clazzOrShortcut + "_" + type, k -> clazzOrShortcut);
         return AccessController.doPrivileged((PrivilegedAction<T>) () -> {
diff --git a/src/main/java/org/opensearch/security/ssl/DefaultSecurityKeyStore.java b/src/main/java/org/opensearch/security/ssl/DefaultSecurityKeyStore.java
index 7ff90c1a66..b697bbedff 100644
--- a/src/main/java/org/opensearch/security/ssl/DefaultSecurityKeyStore.java
+++ b/src/main/java/org/opensearch/security/ssl/DefaultSecurityKeyStore.java
@@ -972,6 +972,7 @@ private void initEnabledSSLCiphers() {
         enabledTransportProtocolsJDKProvider.retainAll(allowedSecureTransportSSLProtocols);
     }
 
+    @SuppressWarnings("removal")
     private SslContext buildSSLServerContext(
         final PrivateKey _key,
         final X509Certificate[] _cert,
@@ -1003,6 +1004,7 @@ public SslContextBuilder run() throws Exception {
         }
     }
 
+    @SuppressWarnings("removal")
     private SslContext buildSSLServerContext(
         final File _key,
         final File _cert,
diff --git a/src/main/java/org/opensearch/security/support/ConfigHelper.java b/src/main/java/org/opensearch/security/support/ConfigHelper.java
index e8526478f2..d9e2921da6 100644
--- a/src/main/java/org/opensearch/security/support/ConfigHelper.java
+++ b/src/main/java/org/opensearch/security/support/ConfigHelper.java
@@ -66,6 +66,7 @@ public static void uploadFile(Client tc, String filepath, String index, CType cT
         uploadFile(tc, filepath, index, cType, configVersion, false);
     }
 
+    @SuppressWarnings("removal")
     public static void uploadFile(
         Client tc,
         String filepath,
diff --git a/src/main/java/org/opensearch/security/support/SecurityIndexHandler.java b/src/main/java/org/opensearch/security/support/SecurityIndexHandler.java
index 1ed8a99614..73af39a348 100644
--- a/src/main/java/org/opensearch/security/support/SecurityIndexHandler.java
+++ b/src/main/java/org/opensearch/security/support/SecurityIndexHandler.java
@@ -87,6 +87,7 @@ public void createIndex(ActionListener<Boolean> listener) {
         }
     }
 
+    @SuppressWarnings("removal")
     public void uploadDefaultConfiguration(final Path configDir, final ActionListener<Set<SecurityConfig>> listener) {
         try (final ThreadContext.StoredContext threadContext = client.threadPool().getThreadContext().stashContext()) {
             AccessController.doPrivileged((PrivilegedAction<Void>) () -> {
diff --git a/src/main/java/org/opensearch/security/util/KeyUtils.java b/src/main/java/org/opensearch/security/util/KeyUtils.java
index 4f03c08cd5..bdf7bf04e0 100644
--- a/src/main/java/org/opensearch/security/util/KeyUtils.java
+++ b/src/main/java/org/opensearch/security/util/KeyUtils.java
@@ -33,6 +33,7 @@
 
 public class KeyUtils {
 
+    @SuppressWarnings("removal")
     public static JwtParserBuilder createJwtParserBuilderFromSigningKey(final String signingKey, final Logger log) {
         final SecurityManager sm = System.getSecurityManager();
 
diff --git a/src/test/java/org/opensearch/security/http/OnBehalfOfAuthenticatorTest.java b/src/test/java/org/opensearch/security/http/OnBehalfOfAuthenticatorTest.java
index 672738326d..bae4fa7f28 100644
--- a/src/test/java/org/opensearch/security/http/OnBehalfOfAuthenticatorTest.java
+++ b/src/test/java/org/opensearch/security/http/OnBehalfOfAuthenticatorTest.java
@@ -67,6 +67,7 @@
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+@SuppressWarnings("removal")
 public class OnBehalfOfAuthenticatorTest {
     final static String clusterName = "cluster_0";
     final static String enableOBO = "true";
diff --git a/src/test/java/org/opensearch/security/tools/democonfig/CertificateGeneratorTests.java b/src/test/java/org/opensearch/security/tools/democonfig/CertificateGeneratorTests.java
index 3b43311679..71771f8116 100644
--- a/src/test/java/org/opensearch/security/tools/democonfig/CertificateGeneratorTests.java
+++ b/src/test/java/org/opensearch/security/tools/democonfig/CertificateGeneratorTests.java
@@ -42,6 +42,7 @@
 import static org.opensearch.security.tools.democonfig.util.DemoConfigHelperUtil.deleteDirectoryRecursive;
 import static org.junit.Assert.fail;
 
+@SuppressWarnings("removal")
 public class CertificateGeneratorTests {
 
     private static Installer installer;
diff --git a/src/test/java/org/opensearch/security/tools/democonfig/InstallerTests.java b/src/test/java/org/opensearch/security/tools/democonfig/InstallerTests.java
index 268bd9ea0e..cef2d79725 100644
--- a/src/test/java/org/opensearch/security/tools/democonfig/InstallerTests.java
+++ b/src/test/java/org/opensearch/security/tools/democonfig/InstallerTests.java
@@ -44,6 +44,7 @@
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.fail;
 
+@SuppressWarnings("removal")
 public class InstallerTests {
     private final ByteArrayOutputStream outContent = new ByteArrayOutputStream();
     private final PrintStream originalOut = System.out;
diff --git a/src/test/java/org/opensearch/security/tools/democonfig/SecuritySettingsConfigurerTests.java b/src/test/java/org/opensearch/security/tools/democonfig/SecuritySettingsConfigurerTests.java
index f4b56e6f76..160d361aef 100644
--- a/src/test/java/org/opensearch/security/tools/democonfig/SecuritySettingsConfigurerTests.java
+++ b/src/test/java/org/opensearch/security/tools/democonfig/SecuritySettingsConfigurerTests.java
@@ -55,6 +55,7 @@
 import static org.opensearch.security.tools.democonfig.util.DemoConfigHelperUtil.deleteDirectoryRecursive;
 import static org.junit.Assert.fail;
 
+@SuppressWarnings("removal")
 @RunWith(com.carrotsearch.randomizedtesting.RandomizedRunner.class)
 public class SecuritySettingsConfigurerTests {
 
diff --git a/src/test/java/org/opensearch/security/tools/democonfig/util/NoExitSecurityManager.java b/src/test/java/org/opensearch/security/tools/democonfig/util/NoExitSecurityManager.java
index 0602812f5d..1b09ecf2dd 100644
--- a/src/test/java/org/opensearch/security/tools/democonfig/util/NoExitSecurityManager.java
+++ b/src/test/java/org/opensearch/security/tools/democonfig/util/NoExitSecurityManager.java
@@ -14,6 +14,7 @@
 /**
  * Helper class to allow capturing and testing exit codes and block test execution from exiting mid-way
  */
+@SuppressWarnings("removal")
 public class NoExitSecurityManager extends SecurityManager {
     @Override
     public void checkPermission(java.security.Permission perm) {