Without digging into sources, since Node is single-threaded, that drastic a performance difference for an IO-bound task would have me looking at whether logging is synchronous. Node's APIs discourage synchronous IO, but don't prevent it.
Zeke mentions this in the comments[0] on the article:
>The console functions are synchronous when the destination is a terminal or a file (to avoid lost messages in case of premature exit) and asynchronous when it’s a pipe (to avoid blocking for long periods of time).
