Is k-means really what people are doing in serious production machine-learning settings?
Yes, that is one option. Ask me over Christmas and I'll tell you a story about a production system using k-means. (Sorry guys, not a story for public consumption.)
More broadly, a lot of machine learning / AI / etc is simpler than people expect under the hood. It's almost a joke in the AI field: as soon as you produce a system that actually works, people say "Oh that's not AI, that's just math."