I'm producing an application with a few peculiar internal communication characteristics that make the usual suspects for data storage and transport (Qs and RDBMSs) ill-fitted. I'm wondering whether there is a product out there that matches the following characteristics:

• all data put into it is peristent
• all reads are delivered out of memory
• data is universally available
• data lives where it is most needed
• data is versioned (nice to have)
• updates are transactional (I'd like ACID characteristics)
• data is potentially replicated, but always in sync
• works on windows
• is based on or has bindings for .NET
• is really fast
• is really robust
• is redundant
• is scalable

I'm looking at things like Microsoft codename "Velocity", but I am not sure whether it fits all of the above characteristics. Likewise, Memcached is not a perfect fit either. The current version of this app opts for an RDBMS with a signaling system for inter-system sync, but latency is too high and versioning of the DB is a pain. I need all the robustness, but with none of the trade-offs.