Colin's done a lot of work in improving boot time on EC2 and in general, so I'm a little surprised he didn't actually mention the boot time in this article. In 2022Q1 he had boot time down to 8s (in EC2, IIRC); based on how cut down the FIRECRACKER config he added is and that there's no loader involvement, I don't think it'd be too surprising if he hits ~5-6s or less.

It took me four days to get the blog post written and I only finished it last night because the toddler went to sleep early. I didn't want to drag it out any longer!

But to answer the question: On small VMs, we can reach /sbin/init in under 50 ms and /etc/rc finishes running in under 500 ms. (Larger VMs take longer -- past a few GB of RAM, the time for initializing paging tables and launching APs starts to dominate.)