diff --git a/server/src/main/java/org/opensearch/cluster/routing/WeightedRouting.java b/server/src/main/java/org/opensearch/cluster/routing/WeightedRouting.java
index 468fac08d2946..6f0e4fe90cfff 100644
--- a/server/src/main/java/org/opensearch/cluster/routing/WeightedRouting.java
+++ b/server/src/main/java/org/opensearch/cluster/routing/WeightedRouting.java
@@ -14,6 +14,7 @@
 import org.opensearch.core.common.io.stream.Writeable;
 
 import java.io.IOException;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
@@ -25,27 +26,26 @@
  */
 @PublicApi(since = "2.4.0")
 public class WeightedRouting implements Writeable {
-    private String attributeName;
-    private Map<String, Double> weights;
+    private final String attributeName;
+    private final Map<String, Double> weights;
+    private final int hashCode;
 
     public WeightedRouting() {
-        this.attributeName = "";
-        this.weights = new HashMap<>(3);
+        this("", new HashMap<>(3));
     }
 
     public WeightedRouting(String attributeName, Map<String, Double> weights) {
         this.attributeName = attributeName;
-        this.weights = weights;
+        this.weights = Collections.unmodifiableMap(weights);
+        this.hashCode = Objects.hash(this.attributeName, this.weights);
     }
 
     public WeightedRouting(WeightedRouting weightedRouting) {
-        this.attributeName = weightedRouting.attributeName();
-        this.weights = weightedRouting.weights;
+        this(weightedRouting.attributeName(), weightedRouting.weights);
     }
 
     public WeightedRouting(StreamInput in) throws IOException {
-        attributeName = in.readString();
-        weights = (Map<String, Double>) in.readGenericValue();
+        this(in.readString(), (Map<String, Double>) in.readGenericValue());
     }
 
     public boolean isSet() {
@@ -70,7 +70,7 @@ public boolean equals(Object o) {
 
     @Override
     public int hashCode() {
-        return Objects.hash(attributeName, weights);
+        return hashCode;
     }
 
     @Override