Some additional comments from Steve, which is cited in the Pinterest example:

I wrote both systems, they had identical architectures
They were implementing the same design as well.

Another fun thing is that the java version had a super fun race condition that would cause people’s notifications to appear in another language. The elixir version simply could not break in that way.

It came down to gc. We had a read path and a write path, both were high volume. I simply could not get Java’s gc to work across both reliably and with the desired latency. I spent a solid month reading the gc manuals, optimizing bits of the system, load testing, and deploying the fixes, and it still suffered horrible tail latency. I had to split the read and write paths into separate services. Worse, due to a shoddy exponential backoff implementation on mobile clients, problems with backend data services would cause request amplification, which would overwhelm and take down the service.
Switching to elixir fixed all these problems. Elixir would just absorb the extra requests and slow down a bit. It never fell over.

It’s disappointing this didn’t get more traction on HN (currently has a few votes and otherwise dropping down the pages of the “new” section). Seems people are eager to discuss how we use a . to call an anonymous function but not how we save companies tons of money. Ah well ¯\(ツ)/¯

Somebody posted the link again and now it got much more engagement.

…And of course, some grumpy people immediately jump in to say that Elixir has nothing that everything else has. And that performance gains are accidental. And that this is not about choosing Elixir but moving away from Rails and Python. Etc.

It’s very rich of them to claim hype and evangelization when it’s them who are always extremely quick to barge in and demean Elixir. Without fail, every time, even though Elixir has probably 3-4 posts on the first page of HN a week. If even that many.

Oh well. I am happy to report that…

…and that my desire to argue in such threads gets less and less and I predict that by next year I won’t even bother. We’ll see.