Exactly this. The individual subsystems can be I/O bound on other subsystems whereas considered as an entire system, it could be CPU-bound. So, yes, one subsy

Exactly this. The individual subsystems can be I/O bound on other subsystems whereas considered as an entire system, it could be CPU-bound. So, yes, one subsystem "blocking" on network I/O definitely is I/O bound regardless of the nature of that I/O, be it database-related or not, it's still I/O. The system at the other end (the db subsystem) may also be I/O (or CPU) bound, but that is distinct from the clients bottleneck.