A surprising number of companies rely on ideas and tools from PL (programming languages) internally. More extreme examples are things like having their own comp

A surprising number of companies rely on ideas and tools from PL (programming languages) internally. More extreme examples are things like having their own compilers and internal languages and more common ones are things like domain-specific languages, static analysis tools and advanced type systems. The thing with PL is that it's something of a meta-field, even within CS: the programs you write help you write other programs. So while user-facing products based on PL ideas are rare (ie just development tools), many companies have surprising numbers of PL people in house who use these tools and techniques internally.