Looking for Blog Post with José Valim Trick

I’m trying to track down a blog post that someone wrote roughly a year ago (I think) that included a trick that José offered up about being more efficient with the data storage for the authors use case.

I want to say that it reminded me of Linux permissions, using binary references to store more than one piece of data in a single integer (as in the read bit is a 4 and a write bit is a 2, so chmod 6 means set the file to be both read and write, two pieces of data represented by a single digit integer).

I went through every article linked from Hugo @ Elixir Radar newsletter thread from last July to now, but no luck. I know this is a big shot in the dark, but wondering if this is enough info to jog someones memory and help me track down the blog post.

Ring a bell?