This framing is misleading. I'm not sure what AI has to do with any of the examples you cited. All of the examples you cited are moves - and in some cases, not even moves, as Shopify is not ditching Ruby - to more performant runtimes and architectures in response to operational concerns at scale, which have a tenuous link to language, and no link to AI that I can see, as these companies all significantly predate LLMs.

Ruby's runtime in the early 2000's compared poorly against the JVM or the BEAM. People used Ruby then and now because it worked well to get products to market quickly. Even after a ton of investment in Ruby's implementation, the JVM and the BEAM are still better able to handle the types of high-traffic, high-concurrency workloads those companies serve, which makes them relevant to mature, high-scale companies.

Tellingly, there are dynamic language implementations that are performance-competitive with static language implementations, like Javascript's V8/Bun/Deno, Lua's LuaJIT, and Common Lisp's SBCL (among others, this is not an exclusive list).

I’ve been using Ruby and Elixir for over a decade. Pre-AI I used them for aesthetic reasons. The code was beautiful, and I disliked dealing with types.

People without experience in dynamic languages tend to overestimate the number of bugs their type system is saving them from. It’s pretty rare that I run into a bug in production that a type system would have caught.

They also overstate how much types help their AI agents write code. I haven’t seen AI write a type related bug in years at this point.

I work with typescript on the front end, and my experience is totally different there. AI is constantly introducing type errors, but only because the original type wasn’t declared properly. Agents waste a ton of time and tokens appeasing typescript. Ruby and Elixir are very token efficient in comparison.

That said, now that I am not writing code by hand anymore, I am considering switching to something like Go. Mainly so I can run my side projects on smaller machines

> Rewriting critical software infrastructure (infostructure) to more reliable typed languages

Instagram (and Threads) is still using Django, which is even slower than Rails. Once you get to unicorn scale, your app is going to bespoke, with some microservices, and super custom stuff. If you can go faster in a gradually typed language, that can be a very good reason to choose one.

> untyped languages are not performant

Typing generally slows down languages, not speed them up because of all the additional checks that must be done. The dynamic stuff is part of what slows down languages like Python and makes them tricky to optimize.

> is there any advantages of using untyped programming language

without any evidence, i claim the corpus might have higher quality variable names and conventions that are "human crutches" around not having types.

LLM knowledge in your non public codebase must be strictly local, and so checking on details and identities of types incurs a cost for the LLM to go fetch that info. if the LLM can "just know" (guess with very high confidence) then thats better for the LLM.

> non-typed languages has more traning data

as per anthropic "poisoning llms with 250 examples" finding, i suspect that corpus size does not really matter that much for any language that is reasonably well used.

Not necessarily. Since the word "typed" language is not well-defined.

For example, typescript is a fantastic language for marshalling data and UI state since it uses substructural typing instead of nominal typing. Libraries like kysely / other ORM libraries are great examples too and easy to use, whereas in fully typed languages like Rust you would end up having to use a macro library like sqlx or having to define structs for each of your types (which would increase compile time & size)

I've used untyped languages extensively, and even built my own, and the errors I get at runtime are almost never type-based, and that's even more true now that LLMs can pump out code. For all the additional ceremony types add, I can't say I've personally realized their benefit.

I don’t understand this question at all. Types are there to prevent human programmers from making a certain class of mistakes. But is the same true for AI. Because if not, static types are just needless cruft.

IMO all of these higher level languages that were designed for humans have a very short lifespan at this point.

The only thing propping them up seems to be loyalty for the most part.

I use Elixir not because of typed/untyped, but because of BEAM and OTP.

Honestly, I think you're framing this incorrectly. Twitter, Airbnd and Shopify all managed to get massive using Ruby on Rails. Maybe that was part of the reason why? I.e. they were able to move fast and developers were happy.

I don't use Rails, so don't have any skin in the game. But who cares if you have to do a re-write once you get to that size?

Rails is still fantastic and handles massive load. 15 percent of all US commerce uses Ruby on Rails

I tried to get into elixir and ruby, but my mind just refuses statically untyped languages apparently.

I'm even less prone to use them with AI.

People no can Rust so people no use Rust. Simple as.