Uber has built its massive driver / rider matching system on Node.js Distributed Web Architecture. Check out the keynote from Uber's Tom Crouche at the Node.js Interactive Conference below. Tom is a senior site reliability engineer and talks about how Node.js is being used at Uber and how future growth requires the community to push the boundaries and expectations for Node.js. Uber’s GitHub page is a good source to also learn more about the company’s most critical systems.
IBM has also embraced NodeJS as well. Myles Borins from IBM spoke about his experiences during this past NodeJS Interactive conference. Here is what he had to say: "During October of 2015 I was given the task of working on The Canary in the Gold Mine, a smoke testing utility that automates running unit tests of various various modules in the node.js ecosystem. CITGM has been incredibly successful, finding all sorts of regressions across the ecosystem and in node core itself.