# UNDF: UNDF-2026-000000745
# UNDF: (leave blank)
--- a/clickhouse-client/src/main/java/com/clickhouse/client/ClickHouseNodes.java
+++ b/clickhouse-client/src/main/java/com/clickhouse/client/ClickHouseNodes.java
@@ -324,10 +324,10 @@ public class ClickHouseNodes implements ClickHouseNodeManager {
      * List of healthy nodes.
      */
-    protected final LinkedList<ClickHouseNode> nodes;
+    protected final LinkedHashSet<ClickHouseNode> nodes;
     /**
      * List of faulty nodes.
      */
-    protected final LinkedList<ClickHouseNode> faultyNodes;
+    protected final LinkedHashSet<ClickHouseNode> faultyNodes;

@@ -373,8 +373,8 @@ public class ClickHouseNodes implements ClickHouseNodeManager {
         this.checking = new AtomicBoolean(false);
         this.index = new AtomicInteger(0);
         this.lock = new ReentrantReadWriteLock();
-        this.nodes = new LinkedList<>(); // usually just healthy nodes
-        this.faultyNodes = new LinkedList<>();
+        this.nodes = new LinkedHashSet<>(); // O(1) contains for load-balancing hot path
+        this.faultyNodes = new LinkedHashSet<>(); // O(1) contains for health check