[cjsplat]

Depending on the numbers involved, previous generation hardware can waterfall to infrastructure apps that are throughput based.

Things accessed through network APIs and billed per op or in aggregate. Distributed file systems, databases, even build and regression suite systems.

Another key point is that older generations of servers for full custom cloud environments tend to co-evolve with their environments. The amount of power and cooling for a rack may not support a modern deployment.

Especially if a generation lasts 6 years. You might be able to cascade gen N+1 to N, but N+6 may require a full retrofit. A 6 year old data center that is partially filled as individual servers fail may justify waiting for N+7 or even 8 to cover the cost of the downtime and retrofit.

There is a reason Google announced that they are depreciating servers over 6 years and Meta is at 5 years, vs the old accounting standard of 3 years.

Then of course there is a secondary market for memory and standard PCI cards, but the market for 6 year old tech is mainly spares, so it is unlikely to absorb the full size of the N-6 year data center build.

If you are considering a refurb style resale market for 6 year old tech, it is often the case that the performance per dollar is a non-starter because of the amount of power the older tech consumes.