But why exactly is an in-memory NoSQL database necessary? This is a "non-sequitur." The fundamental purpose to using NoSQL databases is when your data spans multi-terabytes (where "multi" > 4) and you need replication and slicing. Main-memory NoSQL database seems unnecessary, doesn't it?
Also, when you say "main memory" NoSQL database, are you saying "never store in page file" but always reside/lock in main memory? If it will go to the page file, it's not really main-memory, is it?
Pretty much what I was trying to figure out. I can't see a use case here, since we already have things like Berkeley DB and LevelDB. But main memory? Your use case would have to be such that your entire dataset can fit in memory and for some reason you need extreme performance from that dataset, and from multiple processes running on a single machine. I just don't see it. Is the caching performance of other databases so horrible that this is really necessary?
Also, when you say "main memory" NoSQL database, are you saying "never store in page file" but always reside/lock in main memory? If it will go to the page file, it's not really main-memory, is it?