The m6in.12xlarge is a general-purpose AWS EC2 instance: 48 vCPU and 192 GiB of memory, 4.00 GiB per vCPU. In the name, "m" is the general-purpose line, "6" is the generation, "in" marks Intel processors and enhanced networking and "12xlarge" is the size within the m6in family. It runs on Intel Xeon 8375C (Ice Lake) at 3.5 GHz, and AWS introduced it in November 2022. AWS has since shipped m7i, m8in and m9g; m7i.12xlarge is the direct replacement at this size, scoring 1,068,012 CoreMark/s against this instance's 818,659 — roughly 30% more throughput for the same vCPU count. No single Spot node covers 48 vCPU and 192 GiB, so the equivalent is a fleet: 3 × gp.vs2.2xlarge, 48 vCPU and 192 GiB in total, $3.34/hr on AWS in US East (N. Virginia), from $0.123/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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m6in.12xlarge gives you 48 vCPU and 192 GiB in a single machine. The largest comparable Spot node, gp.vs2.2xlarge, is 16 vCPU and 64 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 192 GiB in one process, it does not.