Recruiter contact through LinkedIn, followed by an initial screening and a couple of phone interviews, which included some basic algorithm questions, scalability, basic OO concepts and some very specific front-end questions (JS).
After these got scheduled for an onsite interview. While in the process, a different team expressed interest (Senior Software position), so I interviewed with both teams on the same day.
Team 1 interviews included a Data Scientist, the Hiring Manager and a Senior Engineer. Questions included understanding of front-end techniques and frameworks (JS, CSS, HTML), and some actual problems the team was dealing with.
Team 2 interviews included basic WS design, scalability and big data, concurrency and other OO concepts. A lunch interview at Walmart's cafe was also included. The interviewer was asking some though questions so it was pretty hard to enjoy lunch.
In general every single engineer working there was extremely friendly and helpful during questioning, with a single exception (the most senior guy interviewing me).
Walmart took care of setting up flights and hotel, and asked to save receipts for them to refund. The coordinators and recruiters handling the process were very professional and helpful and were very good at following up and providing timely updates.
In general Walmart seems to place more focus on specific technologies/techniques knowledge rather than looking for the skills the big players like Google and FB seek (general CS, algorithm and problem solving). The problem with these is that you either know or you don't - it's fairly hard to come up with an answer if you haven't been exposed to them before.
The impression I got is that right now is a good time to join the company - they are trying to rebuild their complete e-commerce infrastructure, so there's opportunities to work in projects from the early stages. Plus, at the scale Walmart demands, the challenge is certainly welcome by any software professional looking to take the next step.