You need to be able to run your system
I fundamentally disagree with the article - sorry! I used to believe it - for many years. But as systems continue to add essential (as opposed to accidental) complexity, the only way to run production is to run production.Why do you want to be able to run the app elsewhere? To test new features? To reduce regressions? Reasonable goals, but at the end of the day the only thing that is identical to production is production. Unless you have a real time copy of all of the data and you continually run copies of all real time production requests, it's not production. It might be the same code and a very similar infrastructure, but without the same data and load, you are going to get regressions in production. Maybe it's flaky historic data or unexpected patterns of load, but whether we like it or not, we're all already testing in production.I'm a huge fan of unit tests, CI, and all of the other common best practices to reduce the number of bugs that are identified in production, but you also need to have the kind of tooling and processes required to minimize recovery time and to be comfortable with testing in production. Small, easily testable, quickly shipped units of work and some flavor of feature flagging so you can dark ship code, recover quickly from outages, and do things like canary roll outs to ensure the new queries don't break with the production data at scale!