The r6g.12xlarge pairs 48 vCPU with 384 GiB of RAM, the 8.00 GiB-per-vCPU ratio that marks a memory-optimized instance. In the name, "r" stands for RAM, "6" is the generation, "g" marks AWS Graviton (ARM) processors and "12xlarge" is the size within the r6g family. It runs on AWS Graviton2 Processor at 2.5 GHz, and AWS introduced it in June 2020. AWS has since shipped r7g, r8g and r9g; r7g.12xlarge is the direct replacement at this size, scoring 1,184,600 CoreMark/s against this instance's 926,402 — roughly 28% more throughput for the same vCPU count. Spot's node ladder tops out below this size, so r6g.12xlarge becomes 3 × mh.vs1.2xlarge (48 vCPU, 384 GiB combined), $2.42/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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r6g.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.
x86_64 onlyr6g.12xlarge is Graviton (arm64) and Rackspace Spot has no arm64 nodes, so you'd be moving to x86. You'll need x86 builds of your images, and per-core speed differs between the chips — worth testing before you decide how many nodes to run.
