Index: oak-blob-cloud/src/main/java/org/apache/jackrabbit/oak/blob/cloud/aws/s3/S3Backend.java
===================================================================
--- oak-blob-cloud/src/main/java/org/apache/jackrabbit/oak/blob/cloud/aws/s3/S3Backend.java	(revision 1752390)
+++ oak-blob-cloud/src/main/java/org/apache/jackrabbit/oak/blob/cloud/aws/s3/S3Backend.java	(working copy)
@@ -18,6 +18,7 @@
 package org.apache.jackrabbit.oak.blob.cloud.aws.s3;
 
 import java.io.File;
+import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
@@ -41,6 +42,8 @@
 import com.google.common.collect.AbstractIterator;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
+
+import org.apache.commons.io.IOUtils;
 import org.apache.jackrabbit.core.data.AsyncTouchCallback;
 import org.apache.jackrabbit.core.data.AsyncTouchResult;
 import org.apache.jackrabbit.core.data.AsyncUploadCallback;
@@ -612,13 +615,26 @@
 
     public void addMetadataRecord(final InputStream input, final String name) throws DataStoreException {
         ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
+        File temp = null;
 
         try {
             Thread.currentThread().setContextClassLoader(getClass().getClassLoader());
+            // spool record to a temporary file so that the size of the data is known
+            // and the stream doesn't need to be buffered in memory. this makes uploading
+            // potentially large records (like the list of blobs marked by the GC)
+            // much more efficient (or even possible).
+            temp = File.createTempFile(getClass().getSimpleName(), "MetadataRecord");
+            try (FileOutputStream os = new FileOutputStream(temp)) {
+                IOUtils.copyLarge(input, os);
+            }
 
             Upload upload = tmx.upload(s3ReqDecorator
-                .decorate(new PutObjectRequest(bucket, addMetaKeyPrefix(name), input, new ObjectMetadata())));
+                .decorate(new PutObjectRequest(bucket, addMetaKeyPrefix(name), temp)));
             upload.waitForUploadResult();
+        } catch (IOException e) {
+            LOG.error("Exception while writing temp file for metadata record [{}], {}",
+                    new Object[] {name, e});
+            throw new DataStoreException("Error in uploading", e);
         } catch (InterruptedException e) {
             LOG.error("Error in uploading", e);
             throw new DataStoreException("Error in uploading", e);
@@ -626,6 +642,9 @@
             if (contextClassLoader != null) {
                 Thread.currentThread().setContextClassLoader(contextClassLoader);
             }
+            if (temp != null) {
+                temp.delete();
+            }
         }
     }