diff --git a/ingestion-sink/src/main/java/com/mozilla/telemetry/ingestion/sink/io/Gcs.java b/ingestion-sink/src/main/java/com/mozilla/telemetry/ingestion/sink/io/Gcs.java
index 837657760..1a7ea81d5 100644
--- a/ingestion-sink/src/main/java/com/mozilla/telemetry/ingestion/sink/io/Gcs.java
+++ b/ingestion-sink/src/main/java/com/mozilla/telemetry/ingestion/sink/io/Gcs.java
@@ -1,6 +1,5 @@
 package com.mozilla.telemetry.ingestion.sink.io;
 
-import com.google.cloud.WriteChannel;
 import com.google.cloud.storage.BlobId;
 import com.google.cloud.storage.BlobInfo;
 import com.google.cloud.storage.Storage;
@@ -10,9 +9,9 @@
 import com.mozilla.telemetry.ingestion.sink.transform.PubsubMessageToObjectNode;
 import com.mozilla.telemetry.ingestion.sink.transform.PubsubMessageToTemplatedString;
 import com.mozilla.telemetry.ingestion.sink.util.BatchWrite;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.UncheckedIOException;
-import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.util.UUID;
@@ -31,6 +30,8 @@ public abstract static class Write extends BatchWrite<PubsubMessage, byte[], Str
 
     public static class Ndjson extends Write {
 
+      private static final byte[] NEWLINE = "\n".getBytes(StandardCharsets.UTF_8);
+
       private final PubsubMessageToObjectNode encoder;
 
       public Ndjson(Storage storage, long maxBytes, int maxMessages, Duration maxDelay,
@@ -43,8 +44,7 @@ public Ndjson(Storage storage, long maxBytes, int maxMessages, Duration maxDelay
       @Override
       protected byte[] encodeInput(PubsubMessage input) {
         try {
-          return ArrayUtils.addAll(Json.asBytes(encoder.apply(input)),
-              "\n".getBytes(StandardCharsets.UTF_8));
+          return ArrayUtils.addAll(Json.asBytes(encoder.apply(input)), NEWLINE);
         } catch (IOException e) {
           throw new UncheckedIOException(e);
         }
@@ -80,7 +80,7 @@ protected Batch getBatch(String gcsPrefix) {
             String.format("Gcs prefix must match \"%s\" but got \"%s\" from: %s",
                 BLOB_ID_PATTERN.pattern(), gcsPrefix, batchKeyTemplate.template));
       }
-      return new Batch(storage, gcsPrefixMatcher.group(BUCKET), gcsPrefixMatcher.group(NAME));
+      return new Batch(gcsPrefixMatcher.group(BUCKET), gcsPrefixMatcher.group(NAME));
     }
 
     @VisibleForTesting
@@ -89,35 +89,24 @@ class Batch extends BatchWrite<PubsubMessage, byte[], String, Void>.Batch {
       @VisibleForTesting
       final BlobInfo blobInfo;
 
-      private final WriteChannel writer;
+      private final ByteArrayOutputStream content = new ByteArrayOutputStream();
 
-      private Batch(Storage storage, String bucket, String keyPrefix) {
+      private Batch(String bucket, String keyPrefix) {
         super();
         // save blobInfo for batchCloseHook
         blobInfo = BlobInfo
             .newBuilder(BlobId.of(bucket, keyPrefix + UUID.randomUUID().toString() + ".ndjson"))
             .setContentType("application/json").build();
-        writer = storage.writer(blobInfo);
       }
 
       @Override
       protected CompletableFuture<Void> close(Void ignore) {
-        try {
-          writer.close();
-        } catch (IOException e) {
-          throw new UncheckedIOException(e);
-        }
-        BlobInfo blobInfoWithSize = storage.get(blobInfo.getBlobId());
-        return batchCloseHook.apply(blobInfoWithSize);
+        return batchCloseHook.apply(storage.create(blobInfo, content.toByteArray()));
       }
 
       @Override
       protected void write(byte[] encodedInput) {
-        try {
-          writer.write(ByteBuffer.wrap(encodedInput));
-        } catch (IOException e) {
-          throw new UncheckedIOException(e);
-        }
+        content.write(encodedInput, 0, encodedInput.length);
       }
 
       @Override
diff --git a/ingestion-sink/src/test/java/com/mozilla/telemetry/ingestion/sink/io/GcsWriteTest.java b/ingestion-sink/src/test/java/com/mozilla/telemetry/ingestion/sink/io/GcsWriteTest.java
index 148b8676b..3dca4d095 100644
--- a/ingestion-sink/src/test/java/com/mozilla/telemetry/ingestion/sink/io/GcsWriteTest.java
+++ b/ingestion-sink/src/test/java/com/mozilla/telemetry/ingestion/sink/io/GcsWriteTest.java
@@ -7,16 +7,12 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.when;
 
-import com.google.cloud.WriteChannel;
 import com.google.cloud.storage.BlobInfo;
 import com.google.cloud.storage.Storage;
 import com.google.pubsub.v1.PubsubMessage;
 import com.mozilla.telemetry.ingestion.sink.transform.PubsubMessageToObjectNode;
 import com.mozilla.telemetry.ingestion.sink.transform.PubsubMessageToTemplatedString;
-import java.io.IOException;
-import java.io.UncheckedIOException;
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.util.concurrent.CompletableFuture;
@@ -37,7 +33,6 @@ public class GcsWriteTest {
 
   private Storage storage;
   private Gcs.Write.Ndjson output;
-  private WriteChannel writer;
 
   private CompletableFuture<Void> batchCloseHook(BlobInfo ignore) {
     return CompletableFuture.completedFuture(null);
@@ -47,8 +42,6 @@ private CompletableFuture<Void> batchCloseHook(BlobInfo ignore) {
   @Before
   public void mockBigQueryResponse() {
     storage = mock(Storage.class);
-    writer = mock(WriteChannel.class);
-    when(storage.writer(any(BlobInfo.class))).thenReturn(writer);
     output = new Gcs.Write.Ndjson(storage, MAX_BYTES, MAX_MESSAGES, MAX_DELAY, BATCH_KEY_TEMPLATE,
         PubsubMessageToObjectNode.Raw.of(), this::batchCloseHook);
   }
@@ -94,19 +87,21 @@ public void canLimitBatchByteSize() {
     assertThat((int) output.batches.get(BATCH_KEY).byteSize, lessThanOrEqualTo(MAX_BYTES));
   }
 
-  @Test(expected = UncheckedIOException.class)
-  public void failsOnInsertErrors() throws Throwable {
-    doThrow(new IOException()).when(writer).close();
-
+  @Test
+  public void failsOnInsertErrors() {
+    final Throwable expect = new RuntimeException("fail");
+    doThrow(expect).when(storage).create(any(BlobInfo.class), any(byte[].class));
+    Throwable cause = null;
     try {
       output.apply(EMPTY_MESSAGE).join();
     } catch (CompletionException e) {
-      throw e.getCause();
+      cause = e.getCause();
     }
+    assertEquals(expect, cause);
   }
 
   @Test
   public void canHandleOversizeMessage() {
-    output.apply(PubsubMessage.newBuilder().putAttributes("meta", "data").build());
+    output.apply(PubsubMessage.newBuilder().putAttributes("meta", "data").build()).join();
   }
 }