Azure Data Lake Store concurrency

I've been toying with Azure Data Lake Store and in the documentation Microsoft claims that the system is optimized for low-latency small writes to files. Testing it out I tried to perform a big amount of writes on parallel tasks to a single file, but this method fails in most cases returning a Bad Request. This link https://issues.apache.org/jira/secure/attachment/12445209/appendDesign3.pdf shows that HDFS isn't made to handle concurrent appends on a single file, so I tried a second time using the ConcurrentAppendAsync method found in the API, but although the method doesn't crash, my file's never modified on the store.