protected boolean isOkToAdd(R request) {
            return requests.size() < config.getMaxBatchSize();
        }
Checks whether it's okay to add the request to this buffer. Called by
{@code addIfAllowed} with a lock on {@code this} held.

@param request
           the request to add
@return true if the request is okay to add, false otherwise
aws-java-sdk-sqs/src/main/java/com/amazonaws/services/sqs/buffered/SendQueueBuffer.java