diff --git a/.circleci/config.yml b/.circleci/config.yml
index eb7c6d17809a..97dd0ecb955a 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -24,7 +24,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -113,10 +113,10 @@ jobs:
   j17_dtests:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -224,7 +224,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 1
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -410,7 +410,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -499,10 +499,10 @@ jobs:
   j11_dtests_latest_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -704,7 +704,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -820,10 +820,10 @@ jobs:
   j17_cqlsh_dtests_py38_vnode:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -930,10 +930,10 @@ jobs:
   j17_dtests_vnode_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1086,10 +1086,10 @@ jobs:
   j11_dtests_vnode_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1221,10 +1221,10 @@ jobs:
   j17_cqlsh_dtests_py311_latest:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1334,7 +1334,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1454,7 +1454,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1546,7 +1546,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1662,10 +1662,10 @@ jobs:
   j11_cqlsh_dtests_py38_latest:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1776,7 +1776,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1864,10 +1864,10 @@ jobs:
   j11_cqlsh_dtests_py311:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -1975,10 +1975,10 @@ jobs:
   j17_dtests_large_vnode_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -2109,10 +2109,10 @@ jobs:
   j17_dtests_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -2268,7 +2268,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -2388,7 +2388,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -2476,10 +2476,10 @@ jobs:
   j17_cqlsh_dtests_py311:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -2586,10 +2586,10 @@ jobs:
   j11_cqlsh_dtests_py38:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -2700,7 +2700,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -2865,7 +2865,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -2957,7 +2957,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -3076,7 +3076,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -3272,10 +3272,10 @@ jobs:
   j11_dtests_large_vnode:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -3362,7 +3362,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -3450,10 +3450,10 @@ jobs:
   j11_dtests_large_vnode_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -3585,10 +3585,10 @@ jobs:
   j11_dtests_large:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -3675,7 +3675,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -3767,7 +3767,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -3884,10 +3884,10 @@ jobs:
   j11_upgrade_dtests_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -4022,7 +4022,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 1
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -4141,7 +4141,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -4336,7 +4336,7 @@ jobs:
   j17_build:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
     parallelism: 1
@@ -4399,6 +4399,7 @@ jobs:
         - .m2
     environment:
     - ANT_HOME: /usr/share/ant
+    - ANT_OPTS: "-Xmx3G"
     - LANG: en_US.UTF-8
     - KEEP_TEST_DIR: true
     - DEFAULT_DIR: /home/cassandra/cassandra-dtest
@@ -4447,7 +4448,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -4567,7 +4568,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -4658,7 +4659,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 1
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -4851,7 +4852,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -4943,7 +4944,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -5214,7 +5215,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -5421,7 +5422,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 1
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -5615,7 +5616,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -5704,10 +5705,10 @@ jobs:
   j17_dtests_vnode:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -5812,10 +5813,10 @@ jobs:
   j11_dtests_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -5950,7 +5951,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6070,7 +6071,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6187,10 +6188,10 @@ jobs:
   j17_dtests_latest_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6324,7 +6325,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6413,10 +6414,10 @@ jobs:
   j11_upgrade_dtests:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6500,10 +6501,10 @@ jobs:
   j11_dtests_large_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6638,7 +6639,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6799,10 +6800,10 @@ jobs:
   j17_dtests_large_vnode:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6885,10 +6886,10 @@ jobs:
   j11_cqlsh_dtests_py38_vnode:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -6999,7 +7000,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -7091,7 +7092,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -7180,10 +7181,10 @@ jobs:
   j11_cqlsh_dtests_py311_latest:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -7356,10 +7357,10 @@ jobs:
   j11_cqlsh_dtests_py311_vnode:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -7470,7 +7471,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -7586,10 +7587,10 @@ jobs:
   j17_cqlsh_dtests_py38_latest:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -7696,10 +7697,10 @@ jobs:
   j17_cqlsh_dtests_py311_vnode:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -7809,7 +7810,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 1
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -7926,10 +7927,10 @@ jobs:
   j17_dtests_latest:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -8037,7 +8038,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -8226,7 +8227,7 @@ jobs:
   j11_build:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
     parallelism: 1
@@ -8289,6 +8290,7 @@ jobs:
         - .m2
     environment:
     - ANT_HOME: /usr/share/ant
+    - ANT_OPTS: "-Xmx3G"
     - LANG: en_US.UTF-8
     - KEEP_TEST_DIR: true
     - DEFAULT_DIR: /home/cassandra/cassandra-dtest
@@ -8338,7 +8340,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -8427,10 +8429,10 @@ jobs:
   j11_dtests_latest:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -8580,10 +8582,10 @@ jobs:
   j11_dtests:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -8667,10 +8669,10 @@ jobs:
   j17_cqlsh_dtests_py38:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -8780,7 +8782,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -8899,7 +8901,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9064,7 +9066,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9152,10 +9154,10 @@ jobs:
   j17_dtests_large:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9241,7 +9243,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9406,7 +9408,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9494,10 +9496,10 @@ jobs:
   j11_dtests_vnode:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11-w-dependencies:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9584,7 +9586,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9672,10 +9674,10 @@ jobs:
   j17_dtests_large_repeat:
     docker:
     - image: apache/cassandra-testing-ubuntu2004-java11:latest
-    resource_class: medium
+    resource_class: large
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9809,7 +9811,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
@@ -9900,7 +9902,7 @@ jobs:
     resource_class: medium
     working_directory: ~/
     shell: /bin/bash -eo pipefail -l
-    parallelism: 4
+    parallelism: 25
     steps:
     - attach_workspace:
         at: /home/cassandra
diff --git a/src/java/org/apache/cassandra/db/compression/ZstdCompressionDictionary.java b/src/java/org/apache/cassandra/db/compression/ZstdCompressionDictionary.java
index a83d1f49106e..bd0b150e2363 100644
--- a/src/java/org/apache/cassandra/db/compression/ZstdCompressionDictionary.java
+++ b/src/java/org/apache/cassandra/db/compression/ZstdCompressionDictionary.java
@@ -20,9 +20,13 @@
 
 import java.time.Instant;
 import java.util.Objects;
+import java.util.Queue;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.atomic.AtomicReference;
 
+import com.github.luben.zstd.ZstdCompressCtx;
+import com.github.luben.zstd.ZstdDecompressCtx;
 import com.github.luben.zstd.ZstdDictCompress;
 import com.github.luben.zstd.ZstdDictDecompress;
 import com.google.common.annotations.VisibleForTesting;
@@ -46,6 +50,12 @@ public class ZstdCompressionDictionary implements CompressionDictionary, SelfRef
     // One ZstdDictDecompress and multiple ZstdDictCompress (per level) can be derived from the same raw dictionary content
     private final ConcurrentHashMap<Integer, ZstdDictCompress> zstdDictCompressPerLevel = new ConcurrentHashMap<>();
     private final AtomicReference<ZstdDictDecompress> dictDecompress = new AtomicReference<>();
+    // Reusable native (de)compression contexts, pooled and borrowed per chunk by compressors sharing this
+    // dictionary. Compress contexts are keyed by level (the loaded CDict is level-specific); decompress contexts
+    // share one pool since a single DDict serves all levels. Closed by Tidy alongside the dictionary tables they
+    // were loaded with, so no context can outlive the native memory it references.
+    private final ConcurrentHashMap<Integer, Queue<ZstdCompressCtx>> compressCtxPoolPerLevel = new ConcurrentHashMap<>();
+    private final Queue<ZstdDecompressCtx> decompressCtxPool = new ConcurrentLinkedQueue<>();
     private volatile Ref<ZstdCompressionDictionary> selfRef;
     private final Instant createdAt;
 
@@ -189,6 +199,100 @@ public ZstdDictDecompress dictionaryForDecompression()
         }
     }
 
+    /**
+     * Borrow a pooled compression context with the dictionary for {@code compressionLevel} already loaded,
+     * creating one if the pool is empty. Reusing a context avoids allocating a native ZSTD_CCtx per call.
+     * <br>
+     * IMPORTANT: Caller MUST hold a valid reference (via tryRef/ref) to this dictionary for as long as the
+     * borrowed context is in use, and must return it via {@link #releaseCompressCtx(int, ZstdCompressCtx)}.
+     *
+     * @param compressionLevel compression level the context should be loaded for
+     * @return a borrowed context; caller owns it exclusively until released
+     * @throws IllegalStateException if called without holding a valid reference
+     */
+    public ZstdCompressCtx acquireCompressCtx(int compressionLevel)
+    {
+        ensureNotReleased();
+        Queue<ZstdCompressCtx> pool = compressCtxPoolPerLevel.computeIfAbsent(compressionLevel, level -> new ConcurrentLinkedQueue<>());
+        ZstdCompressCtx ctx = pool.poll();
+        if (ctx == null)
+            // The compression level is carried by the precomputed CDict, so loadDict is all that is required.
+            ctx = new ZstdCompressCtx().loadDict(dictionaryForCompression(compressionLevel));
+        return ctx;
+    }
+
+    /**
+     * Return a context borrowed from {@link #acquireCompressCtx(int)}. If this dictionary has since been
+     * released, the context is closed instead of pooled, so it does not outlive the dictionary's native memory.
+     */
+    public void releaseCompressCtx(int compressionLevel, ZstdCompressCtx ctx)
+    {
+        Queue<ZstdCompressCtx> pool = compressCtxPoolPerLevel.computeIfAbsent(compressionLevel, level -> new ConcurrentLinkedQueue<>());
+        pool.offer(ctx);
+        if (selfRef == null || selfRef.globalCount() <= 0) // released concurrently — ensure it is not leaked
+            drainCompressPool(pool);
+    }
+
+    /**
+     * Borrow a pooled decompression context with the dictionary already loaded, creating one if the pool is empty.
+     * <br>
+     * IMPORTANT: Caller MUST hold a valid reference (via tryRef/ref) to this dictionary for as long as the
+     * borrowed context is in use, and must return it via {@link #releaseDecompressCtx(ZstdDecompressCtx)}.
+     *
+     * @throws IllegalStateException if called without holding a valid reference
+     */
+    public ZstdDecompressCtx acquireDecompressCtx()
+    {
+        ensureNotReleased();
+        ZstdDecompressCtx ctx = decompressCtxPool.poll();
+        if (ctx == null)
+            ctx = new ZstdDecompressCtx().loadDict(dictionaryForDecompression());
+        return ctx;
+    }
+
+    /**
+     * Return a context borrowed from {@link #acquireDecompressCtx()}. If this dictionary has since been
+     * released, the context is closed instead of pooled.
+     */
+    public void releaseDecompressCtx(ZstdDecompressCtx ctx)
+    {
+        decompressCtxPool.offer(ctx);
+        if (selfRef == null || selfRef.globalCount() <= 0)
+            drainDecompressPool(decompressCtxPool);
+    }
+
+    private static void drainCompressPool(Queue<ZstdCompressCtx> pool)
+    {
+        ZstdCompressCtx ctx;
+        while ((ctx = pool.poll()) != null)
+        {
+            try
+            {
+                ctx.close();
+            }
+            catch (Exception e)
+            {
+                logger.warn("Failed to close pooled ZstdCompressCtx", e);
+            }
+        }
+    }
+
+    private static void drainDecompressPool(Queue<ZstdDecompressCtx> pool)
+    {
+        ZstdDecompressCtx ctx;
+        while ((ctx = pool.poll()) != null)
+        {
+            try
+            {
+                ctx.close();
+            }
+            catch (Exception e)
+            {
+                logger.warn("Failed to close pooled ZstdDecompressCtx", e);
+            }
+        }
+    }
+
     @Override
     public Ref<ZstdCompressionDictionary> tryRef()
     {
@@ -216,7 +320,8 @@ public Ref<ZstdCompressionDictionary> initRefLazily()
             {
                 if (selfRef == null)
                 {
-                    selfRef = new Ref<>(this, new Tidy(zstdDictCompressPerLevel, dictDecompress));
+                    selfRef = new Ref<>(this, new Tidy(zstdDictCompressPerLevel, dictDecompress,
+                                                        compressCtxPoolPerLevel, decompressCtxPool));
                 }
             }
         }
@@ -244,12 +349,18 @@ private static class Tidy implements RefCounted.Tidy
     {
         private final ConcurrentHashMap<Integer, ZstdDictCompress> zstdDictCompressPerLevel;
         private final AtomicReference<ZstdDictDecompress> dictDecompress;
+        private final ConcurrentHashMap<Integer, Queue<ZstdCompressCtx>> compressCtxPoolPerLevel;
+        private final Queue<ZstdDecompressCtx> decompressCtxPool;
 
         Tidy(ConcurrentHashMap<Integer, ZstdDictCompress> zstdDictCompressPerLevel,
-             AtomicReference<ZstdDictDecompress> dictDecompress)
+             AtomicReference<ZstdDictDecompress> dictDecompress,
+             ConcurrentHashMap<Integer, Queue<ZstdCompressCtx>> compressCtxPoolPerLevel,
+             Queue<ZstdDecompressCtx> decompressCtxPool)
         {
             this.zstdDictCompressPerLevel = zstdDictCompressPerLevel;
             this.dictDecompress = dictDecompress;
+            this.compressCtxPoolPerLevel = compressCtxPoolPerLevel;
+            this.decompressCtxPool = decompressCtxPool;
         }
 
         /**
@@ -267,6 +378,13 @@ private static class Tidy implements RefCounted.Tidy
         @Override
         public void tidy()
         {
+            // Close pooled (de)compression contexts BEFORE the dictionary tables they were loaded with, so no
+            // context can outlive the native memory it references.
+            for (Queue<ZstdCompressCtx> pool : compressCtxPoolPerLevel.values())
+                drainCompressPool(pool);
+            compressCtxPoolPerLevel.clear();
+            drainDecompressPool(decompressCtxPool);
+
             // Close all compression dictionaries
             // No synchronization needed - reference counting ensures exclusive access
             for (ZstdDictCompress compressDict : zstdDictCompressPerLevel.values())
diff --git a/src/java/org/apache/cassandra/io/compress/ZstdDictionaryCompressor.java b/src/java/org/apache/cassandra/io/compress/ZstdDictionaryCompressor.java
index 39fb09cd1882..87f292a18452 100644
--- a/src/java/org/apache/cassandra/io/compress/ZstdDictionaryCompressor.java
+++ b/src/java/org/apache/cassandra/io/compress/ZstdDictionaryCompressor.java
@@ -31,6 +31,8 @@
 import com.github.benmanes.caffeine.cache.Caffeine;
 import com.github.benmanes.caffeine.cache.RemovalCause;
 import com.github.luben.zstd.Zstd;
+import com.github.luben.zstd.ZstdCompressCtx;
+import com.github.luben.zstd.ZstdDecompressCtx;
 import com.google.common.annotations.VisibleForTesting;
 
 import org.apache.cassandra.concurrent.ImmediateExecutor;
@@ -51,11 +53,10 @@ public class ZstdDictionaryCompressor extends ZstdCompressorBase implements ICom
             .removalListener((ZstdCompressionDictionary dictionary,
                               ZstdDictionaryCompressor compressor,
                               RemovalCause cause) -> {
-                // Release dictionary reference when compressor is evicted from cache
+                // Release dictionary reference when compressor is evicted from cache. The dictionary's own Tidy
+                // closes any pooled native (de)compression contexts once this was the last reference.
                 if (compressor != null && compressor.dictionaryRef != null)
-                {
                     compressor.dictionaryRef.release();
-                }
             })
             .executor(ImmediateExecutor.INSTANCE)
             .build();
@@ -145,22 +146,39 @@ public int uncompress(byte[] input, int inputOffset, int inputLength, byte[] out
             return super.uncompress(input, inputOffset, inputLength, output, outputOffset);
         }
 
-        int dsz;
+        ZstdDecompressCtx ctx = null;
+        boolean ok = false;
         try
         {
-            dsz = (int) Zstd.decompressFastDict(output, outputOffset,
-                                                input, inputOffset, inputLength,
-                                                dictionary.dictionaryForDecompression());
+            // Reuse a pooled context (dictionary loaded once) rather than the static one-shot, which allocates a
+            // fresh ZSTD_DCtx per call.
+            ctx = dictionary.acquireDecompressCtx();
+            int dsz = ctx.decompressByteArray(output, outputOffset, output.length - outputOffset,
+                                              input, inputOffset, inputLength);
+            if (Zstd.isError(dsz))
+                throw new IOException("Decompression failed due to " + Zstd.getErrorName(dsz));
+            ok = true;
+            return dsz;
+        }
+        catch (IOException e)
+        {
+            throw e;
         }
         catch (Exception e)
         {
             throw new IOException("Decompression failed", e);
         }
-
-        if (Zstd.isError(dsz))
-            throw new IOException("Decompression failed due to " + Zstd.getErrorName(dsz));
-
-        return dsz;
+        finally
+        {
+            // success -> return to pool; failure -> close, so a context that errored is never reused
+            if (ctx != null)
+            {
+                if (ok)
+                    dictionary.releaseDecompressCtx(ctx);
+                else
+                    ctx.close();
+            }
+        }
     }
 
     @Override
@@ -172,19 +190,34 @@ public void uncompress(ByteBuffer input, ByteBuffer output) throws IOException
             return;
         }
 
+        ZstdDecompressCtx ctx = null;
+        boolean ok = false;
         try
         {
-            // Zstd compressors expect only direct bytebuffer. See ZstdCompressorBase.preferredBufferType and supports
-            int decompressedSize = (int) Zstd.decompressDirectByteBufferFastDict(output, output.position(), output.limit() - output.position(),
-                                                                                 input, input.position(), input.limit() - input.position(),
-                                                                                 dictionary.dictionaryForDecompression());
+            // Zstd compressors expect only direct bytebuffer. See ZstdCompressorBase.preferredBufferType and supports.
+            // The context carries the dictionary (loaded once) and is reused across chunks.
+            ctx = dictionary.acquireDecompressCtx();
+            int decompressedSize = ctx.decompressDirectByteBuffer(output, output.position(), output.limit() - output.position(),
+                                                                  input, input.position(), input.limit() - input.position());
             output.position(output.position() + decompressedSize);
             input.position(input.limit());
+            ok = true;
         }
         catch (Exception e)
         {
             throw new IOException("Decompression failed", e);
         }
+        finally
+        {
+            // success -> return to pool; failure -> close, so a context that errored is never reused
+            if (ctx != null)
+            {
+                if (ok)
+                    dictionary.releaseDecompressCtx(ctx);
+                else
+                    ctx.close();
+            }
+        }
     }
 
     @Override
@@ -196,19 +229,34 @@ public void compress(ByteBuffer input, ByteBuffer output) throws IOException
             return;
         }
 
+        ZstdCompressCtx ctx = null;
+        boolean ok = false;
         try
         {
-            // Zstd compressors expect only direct bytebuffer. See ZstdCompressorBase.preferredBufferType and supports
-            int compressedSize = (int) Zstd.compressDirectByteBufferFastDict(output, output.position(), output.limit() - output.position(),
-                                                                             input, input.position(), input.limit() - input.position(),
-                                                                             dictionary.dictionaryForCompression(compressionLevel()));
+            // Zstd compressors expect only direct bytebuffer. See ZstdCompressorBase.preferredBufferType and supports.
+            // The context carries the dictionary (loaded once) and is reused across chunks.
+            ctx = dictionary.acquireCompressCtx(compressionLevel());
+            int compressedSize = ctx.compressDirectByteBuffer(output, output.position(), output.limit() - output.position(),
+                                                             input, input.position(), input.limit() - input.position());
             output.position(output.position() + compressedSize);
             input.position(input.limit());
+            ok = true;
         }
         catch (Exception e)
         {
             throw new IOException("Compression failed", e);
         }
+        finally
+        {
+            // success -> return to pool; failure -> close, so a context that errored is never reused
+            if (ctx != null)
+            {
+                if (ok)
+                    dictionary.releaseCompressCtx(compressionLevel(), ctx);
+                else
+                    ctx.close();
+            }
+        }
     }
 
     @VisibleForTesting