To be fair, I educated the client on the alternatives should 10Gen not improve the aggregation framework so that it could do arbitrary transforms without failure should the output size exceed 16MB. [Use other MongoDB mechanisms, custom compilation with higher per-document size cap, etc.] What annoys me is that 10Gen did not mention this incredibly important limitation when they were touting the planned features of 2.2. My client would not have minded had it simply been the case that queries with large result set sizes were somewhat slow. What this client could not tolerate were failures to deliver any results at all. In retrospect, I wish that I had pushed harder for a solution based on the Hadoop stack. While it seems to have its own demons, at least there is an ecosystem dedicated to fixing the most blatant of limitations.