Zerodha. They are the biggest stock broker in India with a team of less than 40 people. Check out their tech blog for their tech philosophy: https://zerodha.tech/blog/hello-world/
The zerodha post is ... hard to believe. Self managed _everything_ and one devops engineer, no SREs? Who's managing the self-hosted PostgreSQL instances with the hundreds of billions or rows of _financial_ data?
A lot can be said for having an engineering team with the experience and maturity to recognize both strengths and weaknesses of their technology choices.
They wrote a blog post about it but it's been a few years since I read it. IIRC it centered on the inherently stateless request model and how that interacts with the way they wanted to do concurrency.
Also, WhatsApp with their choice of Erlang. https://www.google.com/amp/s/www.wired.com/2015/09/whatsapp-...