Fiddling around with my Emacs configuration tonight, I discovered that the way I specify my default frame font can (paradoxically) have a big impact on my Emacs startup time.
I was picking my font using:
(set-face-attribute 'default nil :family "Fira Code" :height 120)
Which I kinda thought was prohibitively slow. After a little bit of deep Googling, I found another way, namely
(add-to-list 'default-frame-alist '(font . "Fira Code-12"))
This shaves about 0.45 secs off the start-up time.
Why? I have no idea…