this post only links to https://www.reddit.com/r/serverless/ not to an article.
This looks like the intended article.
Edit: Ok, having actually read the actual article now, uh, what? Is this satirical? I have no idea.
Edit 2: Wait, this is posted on IOPipe’s site, which is a technology used in the article. So this is an ad? Weird.
See also https://en.wikipedia.org/wiki/Fibonacci_number#Closed-form_expression for more details on the closed form solution.
I wrote a series of Fibonacci functions at http://chriswarbo.net/blog/2014-07-23-fib.html starting from the naive recursive definition and ending with a co-recursive stream.