Python ORM library for distributed mostly-read-only objects?

[smurfix at gmail.com]

My problem: I have a large database of interconnected objects which I need to process with a combination of short- and long-lived workers. These objects are mostly read-only (i.e. any of them can be changed/marked-as-deleted, but that happens infrequently). The workers may or may not be within one Python process, or even on one system.

I've been doing this with a "classic" session-based SQLAlchemy ORM, approach, but that ends up way too slow and memory intense, as each thread gets its own copy of every object it needs. I don't want that.

My existing code does object loading and traversal by simple attribute access; I'd like to keep that if at all possible.

Ideally, what I'd like to have is an object server which mediates write access to the database and then sends change/invalidation notices to the workers. (Changes are infrequent enough that I don't care if a worker gets a notice it's not interested in.)

I don't care if updates are applied immediately or are only visible to the local process until committed. I also don't need fancy indexing or query abilities; if necessary I can go to the storage backend for that. (That should be SQL, though a NoSQL back-end would be nice to have.)

Does something like this already exist, somewhere out there, or do I need to write this, or does somebody know of an alternate solution?