Jet.com's platform is largely an event driven platform implemented via a microservice architecture. It runs on Microsoft Azure and uses a large number of technologies and middleware. The bulk of backend code is written in F# and their system of record is an event sourced system (essentially a log of all actions on the platform). They use a mix of Redis, Elasticsearch, Azure SQL, Event store and Azure storage for their data stores. About 60% of the platform runs on Linux and the rest windows (although as they move more into Containerization they will see a shift towards Linux further).