Former serious Erlanger here. Lots of comments about performance and scaling in this thread. If you are writing a system for internal use, it's simple scalabili

Former serious Erlanger here. Lots of comments about performance and scaling in this thread. If you are writing a system for internal use, it's simple scalability and robustness make Erlang an excellent choice. Engineers are expensive, machines are cheap. However, if you are writing something that needs massive scalability, the number of machines necessary and the management of it all starts to eclipse engineering cost. Then you need to drop down to a lower level language, or at least something more runtime optimized (like java) for the heavy lifting. Then the costs and frustration of debugging across two languages becomes burdensome. If you are building a competitive commercial product that will be deployed to many customers, the economics start to swing away from Erlang. Customers don't care you needed 1/3 the engineers and testing (or whatever) to get it working. They don't care about how much time and money you saved writing it. They care their EC2 bill is low, or the number of machines in their data center is reduced. A competitor who writes in C might have longer time to market, but they will clobber you when customers see they need 1/4 the machines to support the same workload. Erlang will NEVER be fast. The reason has little to do with the language semantics, and everything to do with it's lack of widespread adoption and therefore lack investment in compilers, runtimes and debugging tools, etc. It's slow because the syntax is ugly and thwarts adoption. If you are a badass VM/complier/JIT/etc engineer, you'll apply your skills to something like Javascript, Java, Python, Ruby, etc and affect a much larger audience. Also the lack of adoption makes Erlang a hard sell in a corporate environments. Sure you might get something up and running much faster, but if your erlangers leave, finding replacements engineers to maintain the system will be tough. I've lived this. I wish I were wrong about it, but 9 years of watching Erlang on the verge of mainstream has jaded me.