Fail to read more than 1M of items with DynamoDBIO

private static class ReadFn<T> extends DoFn<Read<T>, T> {
  @ProcessElement
  public void processElement(@Element Read<T> spec, OutputReceiver<T> out) {
    AmazonDynamoDB client = spec.getAwsClientsProvider().createDynamoDB();
    ScanRequest scanRequest = spec.getScanRequestFn().apply(null);
    scanRequest.setSegment(spec.getSegmentId());
    ScanResult scanResult = client.scan(scanRequest);
    out.output(spec.getScanResultMapperFn().apply(scanResult));
  }
}