Back in the day, traditional databases were often fairly straightforward, such as employee and financial records, unless they needed high-volume, instant access with updates. The airline reservation system was an early model of something that stretched technology. I know someone who worked on that, and it was very hard on the computers and networks of the day.

Now with millions of people online generating immense amounts of data constantly, system designers must account for massive scalability. Think of what's going on behind Netflix and Amazon retail, for example.

Plus the systems are expected to be up all the time.

In my last job, a part of our system that I did not work on was built on older technology, and to do updates of the software, it had to be down for many hours. And this was customer-facing. Bad, bad, bad.