(This is an expanded version of the intro to an article I posted over on the Confluent blog. Here I get to be as verbose as I like ;))
My first job from university was building a datawarehouse for a retailer in the UK. Back then, it was writing COBOL jobs to load tables in DB2. We waited for all the shops to close and do their end of day system processing, and send their data back to the central mainframe.