Does anyone know (from personal experience or official documentation) how many simultaneous requests a single MongoDb server can process before plastering?
If your working set exceeds the amount of RAM that you can afford for a single server, or the disk I / O requirements exceed what you can provide on a single server, or (which is less likely), the requirements for your processor exceed that that you can get on one server, then you need to be fined. It all depends a lot on your specific workload. See http://docs.mongodb.org/manual/faq/storage/#what-is-the-working-set
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