I usually enjoy reading RethinkDB blog posts -- it's unusual for a company with such smart people to write about technical issues they come across -- but I got as far as the first sentence before being disappointed this time.

  On my computer, the callstack of a new process is around 10MB.

I can't imagine what sort of thinking produced this sentence.

First, this limit isn't set by his computer. His computer might affect the limit; but the value is also likely to be affected by his choice of operating systems, his login.conf settings, whether he is root, and possibly environment variables.

Second, processes don't have stacks. Threads have stacks. And often the first thread gets more room than later threads.

Third, the stack starts out small -- like, a few hundred bytes or so, depending on the amount of bloat in his platform's crt1.o (or equivalent). It can grow, of course; but the size of something is not equivalent to its maximum permitted size -- you would never say "a newly created file is 2^64 bytes" just because that's the maximum possible size.

I'd suggest replacing the first sentence with

  On my computer / OS / login environment, the default maximum permitted size of
  the primary thread's stack in a new process is around 10 MB.

(Random side note: You guys have heard of userland threads, right? You seem to be doing an awful lot of wheel-reinventing here -- not necessarily a bad thing, of course, but I didn't find your "threads are too expensive" line particularly convincing.)