[cle]

> The only advantage of clustered systems like Spark, Hadoop, and others is aggregate bandwidth to disk and memory.

Also, aggregate network bandwidth. A major use case for clustered processing is that it is MUCH faster to download external data in parallel across a cluster than in parallel on one box. If timeliness is a major use case of the system you're building, this basically requires a cluster, unless you want to end up re-implementing cluster functionality yourself.