From 4e9e1de4b2146675b4f3ffe52fbdc389ba6c5733 Mon Sep 17 00:00:00 2001
From: RanVaknin <50976344+RanVaknin@users.noreply.github.com>
Date: Thu, 5 Feb 2026 11:39:32 -0800
Subject: [PATCH 1/2] Added cache for computation of partition keys

---
 .../enhanced/dynamodb/mapper/StaticTableMetadata.java       | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableMetadata.java b/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableMetadata.java
index 2126f25dec51..4bdb79d378e6 100644
--- a/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableMetadata.java
+++ b/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableMetadata.java
@@ -23,6 +23,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import software.amazon.awssdk.annotations.NotThreadSafe;
@@ -47,6 +48,7 @@ public final class StaticTableMetadata implements TableMetadata {
     private final Map<String, Object> customMetadata;
     private final Map<String, IndexMetadata> indexByNameMap;
     private final Map<String, KeyAttributeMetadata> keyAttributes;
+    private final ConcurrentHashMap<String, List<String>> partitionKeyCache = new ConcurrentHashMap<>();
 
     private StaticTableMetadata(Builder builder) {
         this.customMetadata = Collections.unmodifiableMap(builder.customMetadata);
@@ -84,6 +86,10 @@ public <T> Optional<T> customMetadataObject(String key, Class<? extends T> objec
 
     @Override
     public List<String> indexPartitionKeys(String indexName) {
+        return partitionKeyCache.computeIfAbsent(indexName, this::computePartitionKeys);
+    }
+
+    private List<String> computePartitionKeys(String indexName) {
         IndexMetadata index = getIndex(indexName);
         
         List<KeyAttributeMetadata> partitionKeys = index.partitionKeys();

From 3ea4dad6e5b71f6966c93ce4def1e221820a852b Mon Sep 17 00:00:00 2001
From: RanVaknin <50976344+RanVaknin@users.noreply.github.com>
Date: Fri, 6 Feb 2026 21:02:05 -0800
Subject: [PATCH 2/2] Add cache for sort key, wrap in unmodifiable list for
 thread safety

---
 .../dynamodb/mapper/StaticTableMetadata.java  | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableMetadata.java b/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableMetadata.java
index 4bdb79d378e6..9f5d985fc8a8 100644
--- a/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableMetadata.java
+++ b/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableMetadata.java
@@ -49,6 +49,7 @@ public final class StaticTableMetadata implements TableMetadata {
     private final Map<String, IndexMetadata> indexByNameMap;
     private final Map<String, KeyAttributeMetadata> keyAttributes;
     private final ConcurrentHashMap<String, List<String>> partitionKeyCache = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<String, List<String>> sortKeyCache = new ConcurrentHashMap<>();
 
     private StaticTableMetadata(Builder builder) {
         this.customMetadata = Collections.unmodifiableMap(builder.customMetadata);
@@ -104,21 +105,25 @@ private List<String> computePartitionKeys(String indexName) {
                                                + "Index name: " + indexName);
         }
 
-        return partitionKeys.stream()
+        return Collections.unmodifiableList(partitionKeys.stream()
                            .filter(Objects::nonNull)
                            .map(KeyAttributeMetadata::name)
-                           .collect(Collectors.toList());
+                           .collect(Collectors.toList()));
     }
 
     @Override
     public List<String> indexSortKeys(String indexName) {
+        return sortKeyCache.computeIfAbsent(indexName, this::computeSortKeys);
+    }
+
+    private List<String> computeSortKeys(String indexName) {
         IndexMetadata index = getIndex(indexName);
-        
+
         List<KeyAttributeMetadata> sortKeys = index.sortKeys();
-        return sortKeys.stream()
-                      .filter(Objects::nonNull)
-                      .map(KeyAttributeMetadata::name)
-                      .collect(Collectors.toList());
+        return Collections.unmodifiableList(sortKeys.stream()
+                       .filter(Objects::nonNull)
+                       .map(KeyAttributeMetadata::name)
+                       .collect(Collectors.toList()));
     }
 
     @Override