Honest question/clarification, is that... considered fast?
My DOS system used to boot that fast. A C64 is almost instant. And my old ~2013 Chromebook boots in ~7 seconds into Linux with an eMMC drive (slower than an SSD but still fairly fast). It's only got 2 GB of RAM so when it hits swap it'll bog to a standstill so it's often faster just to hit the reset key than try and recover.
I'd far rather OOMkiller killed off non active tabs (there's almost always a web browser using the memory on a desktop), or run away apache processses, than try to swap. For that reason I never configure swap on any of my machines.
There are other, more cooperative ways of doing it. For example, always save enough state to restore after a kill when becoming a background task. But it's also more work.
Compared to that, <30 seconds is very fast. SSDs have been a real game-changer, though. My home desktop takes less than 10 seconds from boot manager to display manager. I used to be very patient, now I kind of regret all the time I spent waiting for some computer to boot. ;-)
The C64 boots off ROM, IIRC? So that is kind of cheating. ;-) But yes, I had a C64, too, the delay between switching it on and the machine being usable was too low to notice.
Booting from ROM is one thing. Loading something from tape, that's another story.
I think some C64 units had a spare socket for GEOS the GUI made for the C64.