diff --git a/cardano_node_tests/tests/test_dbsync.py b/cardano_node_tests/tests/test_dbsync.py
index d5a38e728..3bf1868c5 100644
--- a/cardano_node_tests/tests/test_dbsync.py
+++ b/cardano_node_tests/tests/test_dbsync.py
@@ -18,6 +18,7 @@
 from cardano_node_tests.tests import markers
 from cardano_node_tests.utils import cluster_nodes
 from cardano_node_tests.utils import clusterlib_utils
+from cardano_node_tests.utils import configuration
 from cardano_node_tests.utils import dbsync_queries
 from cardano_node_tests.utils import dbsync_service_manager
 from cardano_node_tests.utils import dbsync_snapshot_service
@@ -345,6 +346,8 @@ def test_cost_model(self, cluster: clusterlib.ClusterLib):
         )
 
     @allure.link(helpers.get_vcs_link())
+    # With one instance, run late so shared tests finish before the exclusive lock is needed.
+    @pytest.mark.order(-10 if configuration.CLUSTERS_COUNT < 2 else None)
     @pytest.mark.xdist_split(markers.XdSplits.heavy)
     @pytest.mark.testnets
     def test_reconnect_dbsync(
diff --git a/cardano_node_tests/tests/test_tx_mempool.py b/cardano_node_tests/tests/test_tx_mempool.py
index d1776cb26..d6d6e7c6b 100644
--- a/cardano_node_tests/tests/test_tx_mempool.py
+++ b/cardano_node_tests/tests/test_tx_mempool.py
@@ -10,6 +10,7 @@
 from cardano_node_tests.tests import addrs_common
 from cardano_node_tests.tests import common
 from cardano_node_tests.tests import markers
+from cardano_node_tests.utils import configuration
 from cardano_node_tests.utils import helpers
 
 LOGGER = logging.getLogger(__name__)
@@ -36,6 +37,8 @@ def payment_addrs_locked(
         return addrs
 
     @allure.link(helpers.get_vcs_link())
+    # With one instance, run late so shared tests finish before the exclusive lock is needed.
+    @pytest.mark.order(-10 if configuration.CLUSTERS_COUNT < 2 else None)
     @pytest.mark.xdist_split(markers.XdSplits.heavy)
     @pytest.mark.testnets
     def test_query_mempool_txin(