(And really interesting problems can be really boring to work on, and really interesting companies can have a lot of cruft and technical debt under the hood.)
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.
https://serverless.com/blog/rob-gruhl-serverless-event-sourc...
Here's a recent talk from KubeCon/CloudNativeCon: https://www.youtube.com/watch?time_continue=5&v=xZO9nx6GBu0
Being forward thinking in tech has helped them a lot with regards to being able to move pretty fast on new things. At the same time, a website as old as theirs has a LOT of legacy.
Unfortunately, as this was before the OSS boom that came later, we probably will never see these solutions out in the open.