Title would be more accurate if it said something like "Gitlab: Business Operations - Tech Stack". I was confused for a moment why stuff like Rails and Vue.js weren't mentioned until I realized it's strictly about Business Operations.
This was probably submitted to Hacker News after someone saw my tweet https://mobile.twitter.com/sytses/status/1319325053217992704 which has some questions and answers in the replies.
John already linked to the architecture of GitLab the application in https://news.ycombinator.com/item?id=24869339 in case you are interested in that.
Happy to answer any questions about either.
Some of these applications appear to span both.
Interesting, I thought "back office" was a super-set including both those (ie. CRM-y) tools and coded backend logic when a user makes a requests.
But to your point, there's some grey area here.