"The stuff they used in the good old days" :)

In seriousness, the phrase "boring technology" is, to me, a reference to the talk "Choose Boring Technology" [0], which has been discussed on HN numerous times [1] (deservedly, because it's great).

The author doesn't explicitly say what boring technology is, but uses examples you'd generally expect: postgres, php, python, memcached, mysql, apache web server.

Basically, products that have been doing relatively complicated things (interpreted code, rdbms, key-value stores) for a very long time.

Explicitly, he says that "boring technology" is technology that's defined by its very low maintenance cost. He claims that maintenance costs are mostly driven by uncertainties around failure conditions and design. These kinds of uncertainties are especially present in newer stacks, where the opportunities for footguns and unspecified failure conditions abound, because people are still working them out.

He implicitly references Redis as a fancy new technology, but a lot of people today would probably consider Redis "boring" (unless you're trying to use it as your RDBMS).

[0]: http://boringtechnology.club/

[1]: recently, here: https://news.ycombinator.com/item?id=20323246