Look up what? If I ask a dev the time complexity of a function they’ve just written, what are you expecting them to lookup? They should be able to tell me on the spot and we can discuss if it’s optimal

How does that meme go? Oh yeah: Tell us you haven't read the thread without telling you haven't read the thread.

But, okay, let's entertain your random tangent. Such a request is emblematic of junior managers/junior manager hopefuls misguidedly trying to wedge their knowledge into the function of the operation. In reality, you don't want to have to build a team that requires discussion about such matters. You need to define clear performance requirements upfront and let the benchmarks speak for themselves. Even if a function is O(N!), but measures successfully within the needs of the application, good enough.

It is especially important to encode these requirements in benchmarks as it documents for future developers the same requirements, and ensures they stay within them as code gets modified. The reality is that you won't be around forever. Keeping a team that relies on you to ask such questions is a failing on you.

But let's accept, for the sake of discussion, that you have failed your team. One still does not need to remember that kind of information. The function they wrote contains what they need to know, and they can consult the function to ascertain that information as needed – just as you could all by yourself in this scenario. If you like keeping such trivia in active memory, good on ya, but it is never necessary.

That’s not what this thread chain is about where we’re saying the time complexity for various operations on more obscure but still common data structures (eg btree, trie etc) are trivia that is typically documented by the library providing said data structure. That is distinctly different from being able to perform a big-o analysis on a given piece of code.