But what number would you like to see on a one liner bullet point to indicate “scale, scope, and complexity”?
Super vague, means basically nothing. Maybe it should be written with a bit more detail about what kind of rendering system this is. Still I would be interested, and in the interview I would ask them to explain the system and what they did. However, if it was something stupid (the original code was just super bad) then they would look dumb for bringing it up. Basically, if you put something like this in your CV, it should be something you're proud of for a good reason, not a result of trying to think of anything where you can reduce the impact of your work to a number.
The impact of most work cannot be reduced to a number, so it's perfectly fine to not have any "measurable successes" like that in your CV. In my experience, 75% of people don't, and 75% of people who do have stupid ones that just make them look worse (ie they read online resume-writing advice and put in something like the example this discussion is about). So there is no point in actively trying to think of something like that to put in your CV. If you have something, put it in, if not, that's fine. There's a pretty good way to decide whether to include it: does imagining your interviewer reading it make you feel proud or embarrassed?
But what if you implemented the same rendering system from scratch? If you put in a number, it will mean basically nothing. You can just describe what you built. You don't need to reduce your work to a number. This is simply incorrect advice in the linked blog post. The people hiring you are not judging you based on numbers which claim you contributed to the business in a measureble way. This is simply not true. Ideas like this are usually pushed by people who are not even in SD and are instead self-proclaimed "experts" in the field of "finding jobs" or whatever and are painting all industries with the same brush.
How many people did you work with in your team/department? If you provide internal or public libraries, to how many developers?
I don't think it's shocking to have a line "Worked in the web team with a total of 4 developers in charge of the website of the company (react), backend API (nodeJS), and the Android application."
How would you write that line?
You can make the same argument for user engagement or business metrics numbers too. For most managers reviewing resumes, any number is better than none.
200 queries per second, while pegging 8 CPU cores. Meanwhile my coworker got the short straw implemented a less-used API serving 10 queries, but did it much better than me and used no CPU.
That position is something I should be challenging in the interview with questions to probe deeper:
* Can you tell more about the GraphQL API? Was this new or replacing an API? Tell me about the constraints and goals you were working towards?
* What issues did you have getting to that level of performance? What trade-offs did you make when you hit issues?
* What are the challenges with running your API in production?
* Can the API you implemented scale higher? If so, what would need to be changed with it as you scale to 400 and 1200 queries per second?
If this person has done the work this should be a good discussion and you can start to bring in some of your business or technical problems. It will be very evident whether someone has just invented metrics, or the statement is describing the work of others.
I feel it's important for technical interviewers to have some experience with STAR/behavioral interviewing. This assists with screening/selecting resumes and exploring these areas in interviews.
Hope you don't mind if I steal some of your comment to use in the update of my post! :)