r5a.12xlarge is AWS's memory-optimized EC2 size at 48 vCPU and 384 GiB. In the name, "r" stands for RAM, "5" is the generation, "a" marks AMD processors and "12xlarge" is the size within the r5a family. It runs on AMD EPYC 7571 at 2.5 GHz, and AWS introduced it in November 2018. AWS has since shipped r6a, r7a, r8a and r9g; r6a.12xlarge is the direct replacement at this size, scoring 1,064,184 CoreMark/s against this instance's 635,005 — roughly 68% more throughput for the same vCPU count. The closest Spot shape is mh.vs1.2xlarge at 16 vCPU, so this instance maps to 3 of them — 48 vCPU and 384 GiB across the fleet, $2.71/hr on AWS in US East (N. Virginia), from $0.063/hr on Rackspace Spot. Spot delivers compute as managed Kubernetes, so a node pool of that size is the native shape of the answer rather than a workaround — provided the workload scales horizontally.
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r5a.12xlarge gives you 48 vCPU and 384 GiB in a single machine. The largest comparable Spot node, mh.vs1.2xlarge, is 16 vCPU and 128 GiB, so the equivalent here is 3 nodes rather than one.
Spot runs as managed Kubernetes, so a 3-node pool is the normal way to run things rather than a workaround. If your workload already sits behind a load balancer, a queue or a scheduler, it spreads across them without changes. If it needs all 48 cores and 384 GiB in one process, it does not.
