We're using Haskell to produce an entire compute platform for building, composing, and running type-safe containerised micro-services for data science. This certainly touches on a lot of the areas that Haskell is traditionally known for being good at, e.g. building DSLs, type systems, interpreters, etc.

However, the work also includes a runtime platform that is more low-level, including building our own container system, talking to the Linux kernel, using cgroups/resource management, and distributed message passing - areas where languages such as Go have found a niche, and may be classified as Real World. However for us, Haskell's type-safety, runtime performance, and extensive ecosystem has been a boon even in this domain. We effectively use it as an (incredibly powerful) general-purpose language here, and it's worked more than fine.

We're currently at around 15,000 lines of code with a team of 5 Haskellers, and it hasn't really been a problem regarding performance, understanding the codebase, or with newcomers to the team.

(plug - we're at https://www.github.com/nstack/nstack and are hiring more Haskellers)