The core server technology in WD is being served by Node.js (https://nodejs.org/en/), which act as the integration layer between the various core technologies and services in use. Data storage is handled through the PostgreSQL database, using a mixed model architecture (relational + object based). Our application server runs on Linux, macOS and Windows; our developers typically develop run it on macOS and Windows machine, but for production the application server is deployed on cloud based Linux servers.
In production we host and serve our servers on Linux machines. We use nginx in front of our application servers, where nginx handles specifics around SSL (network transport security), service routing and similar.
Please note that we are currently migrating all our server side software to use docker images and Kubernetes for orchestration. This is done to simplify deployment and make it easier to support private cloud initiatives when required. This will affect all server-side parts of our software, so some of the details about how calculation engines are run server-side might not be entirely accurate. When migration has completed this document will be updated to reflect the actual state of our systems.
For performance reasons, we may also support the capability to run some calculations/simulation engines outside of containerized environments for performance/resource reasons.