I think most people will default to how many hours you put into work. But at what point do we say someone is working hard? Is it working 40hours/week? 50hours/week? or 80-100hours/week?
And how do these hours vary by geography?
I've only ever worked in the Silicon Valley, so my perspective here is very limited (would love for folks to correct me if I'm completely off). Here's my very narrow perspective in very broad strokes:
I think the vast majority of companies, including those in tech, care a lot about perception so raw number of hours worked is more important than actual impact unfortunately. However, even in companies that do actually reward impact, they tend to be FAANG companies or FAANG-equivalent ones, which means that their bar for impact is high, which leads to many hours worked for the majority of engineers working there.
Zooming out, if you're worried about not being perceived as working hard, I would work with your manager if possible to set concrete goals, almost like a contract, around what a good performance review cycle looks like in terms of actual results. From there, you can work backwards from what you actually need to accomplish, not how many hours you need to work.
I have many more thoughts around how you can still achieve great results while working "only" 40 hours a week (or less!) in this Q&A here.