diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -3107,6 +3107,7 @@
     'PhabricatorFileNameTransaction' => 'applications/files/xaction/PhabricatorFileNameTransaction.php',
     'PhabricatorFileQuery' => 'applications/files/query/PhabricatorFileQuery.php',
     'PhabricatorFileROT13StorageFormat' => 'applications/files/format/PhabricatorFileROT13StorageFormat.php',
+    'PhabricatorFileRawDataIteratorFuture' => 'applications/files/data/PhabricatorFileRawDataIteratorFuture.php',
     'PhabricatorFileRawStorageFormat' => 'applications/files/format/PhabricatorFileRawStorageFormat.php',
     'PhabricatorFileSchemaSpec' => 'applications/files/storage/PhabricatorFileSchemaSpec.php',
     'PhabricatorFileSearchConduitAPIMethod' => 'applications/files/conduit/PhabricatorFileSearchConduitAPIMethod.php',
@@ -8835,6 +8836,7 @@
     'PhabricatorFileNameTransaction' => 'PhabricatorFileTransactionType',
     'PhabricatorFileQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorFileROT13StorageFormat' => 'PhabricatorFileStorageFormat',
+    'PhabricatorFileRawDataIteratorFuture' => 'FutureProxy',
     'PhabricatorFileRawStorageFormat' => 'PhabricatorFileStorageFormat',
     'PhabricatorFileSchemaSpec' => 'PhabricatorConfigSchemaSpec',
     'PhabricatorFileSearchConduitAPIMethod' => 'PhabricatorSearchEngineAPIMethod',
diff --git a/src/applications/files/data/PhabricatorFileRawDataIteratorFuture.php b/src/applications/files/data/PhabricatorFileRawDataIteratorFuture.php
new file mode 100644
--- /dev/null
+++ b/src/applications/files/data/PhabricatorFileRawDataIteratorFuture.php
@@ -0,0 +1,67 @@
+<?php
+
+final class PhabricatorFileRawDataIteratorFuture
+  extends FutureProxy {
+
+  private $engine;
+  private $file;
+  private $begin;
+  private $end;
+  private $format;
+
+  public function __construct(
+    PhabricatorFileStorageEngine $engine,
+    PhabricatorFile $file,
+    $begin,
+    $end,
+    PhabricatorFileStorageFormat $format,
+    Future $future) {
+
+    parent::__construct($future);
+
+    $this->engine = $engine;
+    $this->file = $file;
+    $this->begin = $begin;
+    $this->end = $end;
+    $this->format = $format;
+  }
+
+  protected function didReceiveResult($formatted_data) {
+    $file = $this->file;
+    $engine = $this->engine;
+
+    $begin = $this->begin;
+    $end = $this->end;
+    $format = $this->format;
+
+    $known_integrity = $file->getIntegrityHash();
+    if ($known_integrity !== null) {
+      $new_integrity = $engine->newIntegrityHash($formatted_data, $format);
+      if (!phutil_hashes_are_identical($known_integrity, $new_integrity)) {
+        throw new PhabricatorFileIntegrityException(
+          pht(
+            'File data integrity check failed. Dark forces have corrupted '.
+            'or tampered with this file. The file data can not be read.'));
+      }
+    }
+
+    $formatted_data = array($formatted_data);
+
+    $data = '';
+    $format_iterator = $format->newReadIterator($formatted_data);
+    foreach ($format_iterator as $raw_chunk) {
+      $data .= $raw_chunk;
+    }
+
+    if ($begin !== null && $end !== null) {
+      $data = substr($data, $begin, ($end - $begin));
+    } else if ($begin !== null) {
+      $data = substr($data, $begin);
+    } else if ($end !== null) {
+      $data = substr($data, 0, $end);
+    }
+
+    return array($data);
+  }
+
+}
diff --git a/src/applications/files/engine/PhabricatorChunkedFileStorageEngine.php b/src/applications/files/engine/PhabricatorChunkedFileStorageEngine.php
--- a/src/applications/files/engine/PhabricatorChunkedFileStorageEngine.php
+++ b/src/applications/files/engine/PhabricatorChunkedFileStorageEngine.php
@@ -174,6 +174,21 @@
     return (4 * 1024 * 1024);
   }
 
+  public function newRawFileDataIteratorFuture(
+    PhabricatorFile $file,
+    $begin,
+    $end,
+    PhabricatorFileStorageFormat $format) {
+
+    $iterator = $this->getRawFileDataIterator(
+      $file,
+      $begin,
+      $end,
+      $format);
+
+    return new ImmediateFuture($iterator);
+  }
+
   public function getRawFileDataIterator(
     PhabricatorFile $file,
     $begin,
diff --git a/src/applications/files/engine/PhabricatorFileChunkIterator.php b/src/applications/files/engine/PhabricatorFileChunkIterator.php
--- a/src/applications/files/engine/PhabricatorFileChunkIterator.php
+++ b/src/applications/files/engine/PhabricatorFileChunkIterator.php
@@ -10,6 +10,9 @@
   private $end;
   private $data;
 
+  private $queue;
+  private $futures = array();
+
   public function __construct(array $chunks, $begin = null, $end = null) {
     $chunks = msort($chunks, 'getByteStart');
     $this->chunks = $chunks;
@@ -32,11 +35,59 @@
       }
       $this->end = $end;
     }
+
+    $this->queue = array_reverse(array_keys($chunks));
   }
 
   public function current() {
-    $chunk = head($this->chunks);
-    $data = $chunk->getDataFile()->loadFileData();
+    // If the underlying storage engine where the chunk data actually lives
+    // supports futures, we'll try to pre-fetch the next few chunks. If the
+    // engine has relatively high latency relative to its bandwidth (like
+    // Amazon S3), this can improve total throughput rate significantly.
+
+    $limit = 8;
+    while ($this->queue) {
+      if (count($this->futures) >= $limit) {
+        break;
+      }
+
+      $key = array_pop($this->queue);
+      $chunk = $this->chunks[$key];
+
+      $future = $chunk->getDataFile()->newFileDataIteratorFuture();
+      if ($future) {
+        $this->futures[$key] = $future;
+      }
+    }
+
+    $next_key = head_key($this->chunks);
+    if (isset($this->futures[$next_key])) {
+      foreach (new FutureIterator($this->futures) as $future_key => $future) {
+        if ($future_key === $next_key) {
+          break;
+        }
+
+        // NOTE: We don't remove any futures which have already resolved,
+        // because we want to use only a constant amount of memory. If we free
+        // up the slots of resolved futures, we might get more throughput, but
+        // could end up with the entire file buffered in memory if the storage
+        // engine can send data to us faster than the client can read it.
+
+      }
+    }
+
+    $chunk = $this->chunks[$next_key];
+    $chunk_future = idx($this->futures, $next_key);
+    unset($this->futures[$next_key]);
+
+    if ($chunk_future) {
+      $data = '';
+      foreach ($chunk_future->resolve() as $piece) {
+        $data .= $piece;
+      }
+    } else {
+      $data = $chunk->getDataFile()->loadFileData();
+    }
 
     if ($this->end !== null) {
       if ($chunk->getByteEnd() > $this->end) {
diff --git a/src/applications/files/engine/PhabricatorFileStorageEngine.php b/src/applications/files/engine/PhabricatorFileStorageEngine.php
--- a/src/applications/files/engine/PhabricatorFileStorageEngine.php
+++ b/src/applications/files/engine/PhabricatorFileStorageEngine.php
@@ -179,7 +179,6 @@
    */
   abstract public function readFile($handle);
 
-
   /**
    * Delete the data for a file previously written by @{method:writeFile}.
    *
@@ -327,42 +326,38 @@
     return $engine->getChunkSize();
   }
 
-  public function getRawFileDataIterator(
+  public function newRawFileDataIteratorFuture(
     PhabricatorFile $file,
     $begin,
     $end,
     PhabricatorFileStorageFormat $format) {
 
-    $formatted_data = $this->readFile($file->getStorageHandle());
-
-    $known_integrity = $file->getIntegrityHash();
-    if ($known_integrity !== null) {
-      $new_integrity = $this->newIntegrityHash($formatted_data, $format);
-      if (!phutil_hashes_are_identical($known_integrity, $new_integrity)) {
-        throw new PhabricatorFileIntegrityException(
-          pht(
-            'File data integrity check failed. Dark forces have corrupted '.
-            'or tampered with this file. The file data can not be read.'));
-      }
-    }
+    return new PhabricatorFileRawDataIteratorFuture(
+      $this,
+      $file,
+      $begin,
+      $end,
+      $format,
+      $this->newRawReadFuture($file->getStorageHandle()));
+  }
 
-    $formatted_data = array($formatted_data);
+  public function getRawFileDataIterator(
+    PhabricatorFile $file,
+    $begin,
+    $end,
+    PhabricatorFileStorageFormat $format) {
 
-    $data = '';
-    $format_iterator = $format->newReadIterator($formatted_data);
-    foreach ($format_iterator as $raw_chunk) {
-      $data .= $raw_chunk;
-    }
+    $future = $this->newRawFileDataIteratorFuture(
+      $file,
+      $begin,
+      $end,
+      $format);
 
-    if ($begin !== null && $end !== null) {
-      $data = substr($data, $begin, ($end - $begin));
-    } else if ($begin !== null) {
-      $data = substr($data, $begin);
-    } else if ($end !== null) {
-      $data = substr($data, 0, $end);
-    }
+    return $future->resolve();
+  }
 
-    return array($data);
+  protected function newRawReadFuture($handle) {
+    return new ImmediateFuture($this->readFile($handle));
   }
 
   public function newIntegrityHash(
diff --git a/src/applications/files/engine/PhabricatorS3FileStorageEngine.php b/src/applications/files/engine/PhabricatorS3FileStorageEngine.php
--- a/src/applications/files/engine/PhabricatorS3FileStorageEngine.php
+++ b/src/applications/files/engine/PhabricatorS3FileStorageEngine.php
@@ -89,24 +89,13 @@
    * Load a stored blob from Amazon S3.
    */
   public function readFile($handle) {
-    $s3 = $this->newS3API();
-
-    $profiler = PhutilServiceProfiler::getInstance();
-    $call_id = $profiler->beginServiceCall(
-      array(
-        'type' => 's3',
-        'method' => 'getObject',
-      ));
-
-    $result = $s3
-      ->setParametersForGetObject($handle)
-      ->resolve();
-
-    $profiler->endServiceCall($call_id, array());
-
-    return $result;
+    return $this->newRawReadFuture()->resolve();
   }
 
+  protected function newRawReadFuture($handle) {
+    return $this->newS3API()
+      ->setParametersForGetObject($handle);
+  }
 
   /**
    * Delete a blob from Amazon S3.
diff --git a/src/applications/files/storage/PhabricatorFile.php b/src/applications/files/storage/PhabricatorFile.php
--- a/src/applications/files/storage/PhabricatorFile.php
+++ b/src/applications/files/storage/PhabricatorFile.php
@@ -786,6 +786,15 @@
     return $this->loadDataFromIterator($iterator);
   }
 
+  public function newFileDataIteratorFuture($begin = null, $end = null) {
+    $engine = $this->instantiateStorageEngine();
+    $format = $this->newStorageFormat();
+    return $engine->newRawFileDataIteratorFuture(
+      $this,
+      $begin,
+      $end,
+      $format);
+  }
 
   /**
    * Return an iterable which emits file content bytes.
@@ -795,17 +804,8 @@
    * @return Iterable Iterable object which emits requested data.
    */
   public function getFileDataIterator($begin = null, $end = null) {
-    $engine = $this->instantiateStorageEngine();
-
-    $format = $this->newStorageFormat();
-
-    $iterator = $engine->getRawFileDataIterator(
-      $this,
-      $begin,
-      $end,
-      $format);
-
-    return $iterator;
+    return $this->newFileDataIteratorFuture($begin, $end)
+      ->resolve();
   }
 
   public function getURI() {