I do confirm this behavior.
Transactions and asynchronous updates may seem antagonistic, but they are not on a multi-level cache.
I plan to use a synchronous transactional disk cache and a second non transactional asynchronous s3 cache, to get the best of both worlds.
Since the asynchronous aspect of the s3 cache will not allow me to get any feedback (aka Future), I want it to 'write-behind' in the background (and hope everything goes well).
I will wait for the qi4j v1 release (probably Monday), adapt infinispan to the blobstore of jClouds and take a closer look at this in a couple of weeks.