Jane Street are looking for Software Engineers who want to help design and build the systems and tools that run the firm. You’ll find Software Engineers in all parts of Jane Street, solving real problems in critical areas ranging from trading desks to accounting, as well as building foundational infrastructure, whether that means implementing network monitoring or risk models. Jane Street are big believers in functional programming, and use OCaml as their primary development language (with the largest team of OCaml developers in any industrial setting). Jane Street recognises the value of open source software, leveraging it within daily work and releasing hundreds of thousands of lines of their own code as open source. They're always exploring new ways to expand open source projects, and provide ongoing support to things like Mercurial, the OCaml compiler, and the OPAM package manager.