Walmart is so large, they're projecting to save $200 million per year on energy costs by switching to all-LED lighting and away from fluorescent lighting in their stores, parking lots, etc. That savings is almost equivalent to the full-year operating income for Salesforce.com in their last fiscal year ($235m).
The $15b gain in sales was in part due to ecommerce gains, while physical retail remained steady with modest same store sales gains. Thanks in part to the Jet.com acquisition, they grew by 44% online in 2017 (fourth quarter online growth dropped to 23%, with the Jet.com boost rolling past). They've been going around buying up independent retail brands, like ModCloth, Bare Necessities, Bonobos. They view that brand accumulation as building up a moat vs Amazon, I'd expect them to continue with that.
The most interesting thing about Amazon today, is that at least 3/4 of the value in their business is outside of traditional retail. Their relatively young ad business will be worth more than their retail business within a year or two (if it's not already). Sometimes I think Alibaba was their primary inspiration for going aggressively that direction, more so than Google or Facebook. With enough of a thriving ad business on top of retail, they can do things no other normal retailer can ever do when it comes to margins, they can safely take their margin in retail to zero (ie intentionally yield zero profit in retail, and build an ad business as big and profitable as Facebook's). Walmart can't compete with that tactic, it'll draw intense anti-trust scrutiny over time if they do it.
Competing with Amazon has helped push Walmart's annual profit down considerably over time, despite sales doing well: $15.9b (fiscal 2014 profit), $16.3b, $14.7b, $13.6b, $9.8b (fiscal 2018). If Amazon uses the nuclear option on margins with a thriving ad business (not to mention AWS) as a profit buffer, they might be able to push Walmart into losing money in retail in a price fight. I'll be curious to see if that's the direction Amazon goes competitively.
I spend four to five hours per day reading and have a very strong memory, so I hoover up a lot and remember most of the things I read. No particular focus on Walmart.