Their tech stack is similar to what you'd expect from any large tech company. I can't speak much to the server side of things (I worked on the iOS app) but I know they had everything ranging from older monolithic .NET apps to Node and Go micro services.

Their GitHub page (https://github.com/Nordstrom) doesn't have much in the way of internal projects, but it has lots of forks that will give you an idea of some of the tools they used.