diff --git a/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java b/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
index ae8269d..c454e41 100644
--- a/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
+++ b/block-storage/src/main/java/org/lucares/pdb/map/PersistentMap.java
@@ -153,7 +153,10 @@ public class PersistentMap<K, V> implements AutoCloseable {
 
     private final LRUCache<Long, PersistentMapDiskNode> nodeCache = new LRUCache<>(10_000);
 
-    private final LRUCache<K, V> valueCache = new LRUCache<>(1_000);
+    private final LRUCache<K, V> valueCache = new LRUCache<>(10_000);
+
+    // guarded by: this
+    private volatile long nodeOffsetOfRootNode = -1;
 
     public PersistentMap(final Path path, final Path storageBasePath, final EncoderDecoder<K> keyEncoder,
             final EncoderDecoder<V> valueEncoder) {
@@ -161,6 +164,9 @@ public class PersistentMap<K, V> implements AutoCloseable {
         this.keyEncoder = keyEncoder;
         this.valueEncoder = valueEncoder;
         initIfNew();
+
+        final DiskBlock diskBlock = diskStore.getDiskBlock(NODE_OFFSET_TO_ROOT_NODE, diskStore.minAllocationSize());
+        nodeOffsetOfRootNode = diskBlock.getByteBuffer().getLong(0);
     }
 
     @Override
@@ -478,15 +484,14 @@ public class PersistentMap<K, V> implements AutoCloseable {
     }
 
     private long readNodeOffsetOfRootNode() {
-        final DiskBlock diskBlock = diskStore.getDiskBlock(NODE_OFFSET_TO_ROOT_NODE, diskStore.minAllocationSize());
-
-        return diskBlock.getByteBuffer().getLong(0);
+        return nodeOffsetOfRootNode;
     }
 
     private void writeNodeOffsetOfRootNode(final long newNodeOffsetToRootNode) {
         final DiskBlock diskBlock = diskStore.getDiskBlock(NODE_OFFSET_TO_ROOT_NODE, diskStore.minAllocationSize());
         diskBlock.getByteBuffer().putLong(0, newNodeOffsetToRootNode);
         diskBlock.force();
+        nodeOffsetOfRootNode = newNodeOffsetToRootNode;
     }
 
 }