The c7g.medium is a compute-optimized AWS EC2 instance: 1 vCPU and 2 GiB of memory, 2.00 GiB per vCPU. In the name, "c" stands for compute, "7" is the generation, "g" marks AWS Graviton (ARM) processors and "medium" is the size within the c7g family. It runs on AWS Graviton3 Processor at 2.5 GHz, and AWS introduced it in May 2022. AWS has since shipped c8g and c9g; c8g.medium is the direct replacement at this size, scoring 30,161 CoreMark/s against this instance's 24,828 — roughly 21% more throughput for the same vCPU count. The nearest Spot node is ch.vs2.medium at 2 vCPU and 4 GiB — 1 more vCPU and 2 GiB more memory, about 94% below the US East (N. Virginia) on-demand rate.
Match qualityx86 substitution
c7g.medium is Graviton (arm64). Rackspace Spot does not have arm64 servers, so ch.vs2.medium is an x86_64 substitute with similar specs.
You will need x86 builds of your container images. Most software rebuilds without changes, but anything with compiled native code needs a real rebuild rather than a retag. Speed per core also differs between the two chips, so it is worth testing before deciding how many nodes to run.