15 years ago I was working at a utility and was re-architecting our meter-data solution as the state government was about to mandate a change from manually read meters to remotely read interval meters. Had to rescale the database from processing less than 2 million reads a year, to over 50 million reads _a day_ (for our roughly 1M meters). Needed to keep 16 months online, and several years worth in near-line storage. We went from a bog-standard Oracle database to Oracle Enterprise with partitions by month. This was being fed by an event-driven microservices[0] architecture of individually deployable Pro*C/C++ unix executables. The messaging was Oracle A/Q.

At the time, I thought "wow - this is big!", and it was for me.

[0] we didn't call it microservices back then though that's clearly what it was. The term I used was "event-driven, loosely coupled, transactional programs processing units of work comprised of a day's worth of meter readings per meter". Doesn't roll off the tongue quite so easily.