Redlining RAM + CPU is not difficult for the right kind of database application that needs in-memory latency. RAM is a limit on your (hot, at least) data size, and CPU is a limit on your query workload.
In my experience, harder to also balance I/O so you’re close to hitting three limits, but update-heavy transactional workloads can manage it for disk-based DBMS’s.
In my experience, harder to also balance I/O so you’re close to hitting three limits, but update-heavy transactional workloads can manage it for disk-based DBMS’s.