SimCorp is the largest industrial user of APL I know of. They even own part of Dyalog. They mostly use APL for business logic written by domain experts (prima

SimCorp is the largest industrial user of APL I know of. They even own part of Dyalog. They mostly use APL for business logic written by domain experts (primarily people who studied finance), while infrastructure and GUIs tends to be written in C# by trained programmers.