When I was working in a queue feature (for example to buy tailor swift ticket), and was proud of my complicated real-time solution using websockets and CRDTs...then a more experienced guy came, rearchitected in a much simpler way using just the DB with long-polling, not real real-time (but who cares), and it ended up simpler to deal with network splits or crashes. Learned the hard way you can never rely on the networ…
One of the earliest projects I took over from a higher level developer was an auction website back around 1998. The site worked like eBay in as far as you could put a maximum bid, and it would automatically bid higher than the last bid up to that point. The problem was, it was all dependent on users being on that page so that the auto-reload http header would fire again and refresh the page. If nobody was on the site…
Big website, no problem. Small internet site, big problem.
(Yes, for some cron + wget/curl was whipped out)