diff --git a/hudi-common/src/main/java/org/apache/hudi/common/util/DefaultSizeEstimator.java b/hudi-common/src/main/java/org/apache/hudi/common/util/DefaultSizeEstimator.java
index 0e6d78f1f224d..8032a04df4647 100644
--- a/hudi-common/src/main/java/org/apache/hudi/common/util/DefaultSizeEstimator.java
+++ b/hudi-common/src/main/java/org/apache/hudi/common/util/DefaultSizeEstimator.java
@@ -18,12 +18,14 @@
 
 package org.apache.hudi.common.util;
 
+import java.io.Serializable;
+
 /**
  * Default implementation of size-estimator that uses Twitter's ObjectSizeCalculator.
  * 
  * @param <T>
  */
-public class DefaultSizeEstimator<T> implements SizeEstimator<T> {
+public class DefaultSizeEstimator<T> implements SizeEstimator<T>, Serializable {
 
   @Override
   public long sizeEstimate(T t) {
diff --git a/hudi-common/src/main/java/org/apache/hudi/common/util/HoodieRecordSizeEstimator.java b/hudi-common/src/main/java/org/apache/hudi/common/util/HoodieRecordSizeEstimator.java
index 78f7b1b9bb105..88a0f70cd831c 100644
--- a/hudi-common/src/main/java/org/apache/hudi/common/util/HoodieRecordSizeEstimator.java
+++ b/hudi-common/src/main/java/org/apache/hudi/common/util/HoodieRecordSizeEstimator.java
@@ -26,12 +26,14 @@
 import org.apache.log4j.LogManager;
 import org.apache.log4j.Logger;
 
+import java.io.Serializable;
+
 /**
  * Size Estimator for Hoodie record payload.
  * 
  * @param <T>
  */
-public class HoodieRecordSizeEstimator<T extends HoodieRecordPayload> implements SizeEstimator<HoodieRecord<T>> {
+public class HoodieRecordSizeEstimator<T extends HoodieRecordPayload> implements SizeEstimator<HoodieRecord<T>>, Serializable {
 
   private static final Logger LOG = LogManager.getLogger(HoodieRecordSizeEstimator.class);
 
diff --git a/hudi-common/src/main/java/org/apache/hudi/common/util/collection/ExternalSpillableMap.java b/hudi-common/src/main/java/org/apache/hudi/common/util/collection/ExternalSpillableMap.java
index a6e8d5cfb35c0..8d2707d6045bb 100644
--- a/hudi-common/src/main/java/org/apache/hudi/common/util/collection/ExternalSpillableMap.java
+++ b/hudi-common/src/main/java/org/apache/hudi/common/util/collection/ExternalSpillableMap.java
@@ -52,7 +52,7 @@
  * map may occupy more memory than is available, resulting in OOM. However, if the spill threshold is too low, we spill
  * frequently and incur unnecessary disk writes.
  */
-public class ExternalSpillableMap<T extends Serializable, R extends Serializable> implements Map<T, R> {
+public class ExternalSpillableMap<T extends Serializable, R extends Serializable> implements Map<T, R>, Serializable {
 
   // Find the actual estimated payload size after inserting N records
   private static final int NUMBER_OF_RECORDS_TO_ESTIMATE_PAYLOAD_SIZE = 100;
diff --git a/hudi-common/src/main/java/org/apache/hudi/common/util/collection/RocksDBBasedMap.java b/hudi-common/src/main/java/org/apache/hudi/common/util/collection/RocksDBBasedMap.java
index c4fbd3a8cb0db..67b4ffabe2e57 100644
--- a/hudi-common/src/main/java/org/apache/hudi/common/util/collection/RocksDBBasedMap.java
+++ b/hudi-common/src/main/java/org/apache/hudi/common/util/collection/RocksDBBasedMap.java
@@ -29,12 +29,12 @@
 /**
  * A map's implementation based on RocksDB.
  */
-public final class RocksDBBasedMap<K extends Serializable, R extends Serializable> implements Map<K, R> {
+public final class RocksDBBasedMap<K extends Serializable, R extends Serializable> implements Map<K, R>, Serializable {
 
   private static final String COL_FAMILY_NAME = "map_handle";
 
   private final String rocksDbStoragePath;
-  private RocksDBDAO rocksDBDAO;
+  private transient RocksDBDAO rocksDBDAO;
   private final String columnFamilyName;
 
   public RocksDBBasedMap(String rocksDbStoragePath) {