Oblique strategies is a clever take on generating ideas — really, read the wikipedia article. In homage to it I have been collecting my own set of "oblique questions": questions that apply to engineering problems to get a different perspective on them. (They are way less cool than oblique strategies so please forgive me for stealing the name.)
The power of the questions is that they are simultaneously vague enough to apply to many situations while also still prompting interesting answers.
What would we do if we had 1/10th the resources?
(By 'resources' here I mean 'engineers', but it also works with interpretations like RAM/CPU.)
For example, suppose you're building a photo hosting app, and someone suggests step one is to build a new kind of database. What would we do if we had 1/10th the resources? We'd take PostgreSQL off the shelf and focus on the problems that our users care about.
For example, suppose you're building an app for platform X, the tools for building apps for platform X aren't great, and someone suggests building a new programming language. What would we do if we had 1/10th the resources? We'd look at what other people had done to succeed on that platform and use their approach instead.
The point here isn't to say that you should never invent a new database system or programming language, but rather that by asking the question, you're asking what part of the work is truly core to the problem you're solving, and which parts aren't as necessary. And much in the same way that scaling a system by 10x may require a new architecture, scaling a system to 0.1x also lets you frame fundamental questions about your architecture. Maybe realtime updates aren't worth their implementation cost; maybe we don't need to make native mobile versions of an app that will have at most 1000 users.
This question is also often prescient. Even if you have many engineers around now eager to invent your new database system, how do you expect to be able to continue to fund ongoing maintenance? What will you do when you inevitably have 1/10th the team in the future and are tasked with keeping the system alive and competitive?
What would we do if we didn't have this and someone gave it to us?
For example, imagine two applications A and B that are identical except in one way: application A has an additional test suite that collects a set of slow, flaky tests, which require painful manual updates.
Now suppose someone showed up to B with a patch making it like A: "Hey, this patch adds a bunch of tests. Note: they take a very long time to run, when they fail it doesn't necessarily mean something is wrong, and when you change things in the app you will have to do a lot of tedious work to update them. Oh and also, though I'm giving you the code now, you're on the hook forever for keeping it going into the future." Would you accept the patch? I wouldn't. And if that is so, you could reasonably argue you should also just delete the tests in application A.
Loss aversion and sunk costs are the broader ideas here. Even though you invested a lot of resources in making a bad test suite, that investment is in the past and irreversible. Today, the right way to evaluate whether it's worth keeping is by the framing presented by application B above.
Another example of where this applies is in evaluating options and rarely-used features. A coworker told a great story of a Google-internal system that had a UI feature that was very difficult to implement, requiring complex distributed systems solutions that were costly in performance and cognitive overhead, and how over the years they were rewarded for improving the system in various ways. Only later, they realized they could have just removed the UI feature, which wasn't that important in the first place.
Who if not you?
For example, suppose someone wants to deprecate API A in favor of API B. But there's a lot of code lingering around that still uses API A. Often, the author of A will try something like: "I cannot possibly fix all the code that uses API A. We can just mark it deprecated and then people can migrate on their own later".
To that I ask: Who if not you? If you don't have time to do this migration now — if it's not so important that you would prioritize doing it — why would you expect someone else would have this time later? Because usually the result of an incomplete migration is just that you end up supporting both API A and B forever.
Another place I often ask this is when I find someone junior complaining about some broken system: Who will fix it if you don't? This question is about trying to help people take ownership, and to realize that they are participants, not just consumers. Oftentimes "fixing" a problem might just be taking the effort to surface the issue in the right forum — for example, perhaps the team behind the system isn't even aware of the problem.
The most important person question to ask this question of is yourself. If you notice something wrong, who will fix it if not you? Usually the answer is "nobody" unless you take action.
What are we trading off?
Engineering is fundamentally about making smart tradeoffs. At the small scale we talk about trading off RAM for CPU, but at the larger scale we also trade off correctness for speed, or time to ship vs technical debt. If someone presents something with the claim that it's all benefits and no costs — or the reverse — what that really means is that they don't fully understand the problem space.
Often that misunderstanding is due to not appreciating the total scope of problem space, which encompasses not only specific technology choices but also time factors (how will this solution work over five years? will maintenance be a problem? will a piece we rely upon be abandoned?) and human factors (again: what will happen when we have 1/10th the resources?).
Exercise: imagine the technology you like the least (Go? PHP? Electron?) and try to make a genuine argument for why someone might use it and be right.