The x1e.4xlarge pairs 16 vCPU with 488 GiB of RAM, the 30.50 GiB-per-vCPU ratio that marks a memory-optimized instance. In the name, "x" is the extra-memory line, "1" is the generation, "e" marks extended capacity and "4xlarge" is the size within the x1e family. It runs on High Frequency Intel Xeon E7-8880 v3 (Haswell) at 2.3 GHz, and AWS introduced it in November 2017. AWS has since shipped x2gd and x8i; x2gd.4xlarge is the direct replacement at this size, scoring 317,523 CoreMark/s against this instance's 276,948 — roughly 15% more throughput for the same vCPU count. Spot's node ladder tops out below this size, so x1e.4xlarge becomes 4 × mh.vs1.2xlarge (64 vCPU, 512 GiB combined), $3.34/hr on AWS in US East (N. Virginia), from $0.084/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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x1e.4xlarge gives you 16 vCPU and 488 GiB in a single machine. The largest comparable Spot node, mh.vs1.2xlarge, is 16 vCPU and 128 GiB, so the equivalent here is 4 nodes rather than one.
Spot runs as managed Kubernetes, so a 4-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 16 cores and 488 GiB in one process, it does not.
No local diskx1e.4xlarge comes with 1 × 480 GB SSD attached to the machine. Spot nodes use network storage only, so that disk doesn't come with it. If you were using it as fast scratch space, you'd move to a persistent volume or object storage, which are slower to read.