What is the difference between a Senior and Staff engineer in a System Design Interview?

I highly recommend going through this thread if you haven't already: "Quality to demonstrate for staff MLE during interview?"

A couple important caveats:

• System design interviews vary wildly based on stack. The system design rounds I go through as an Android/product engineer are very different from those a backend engineer or MLE would go through. My answer will be anchored more towards the product side.
• From my experience, senior and staff senior system design interview performances feel like a more iterative difference vs. a transformative one. For the most part, staff engineers are sharpening the positive traits they developed at the senior level as opposed to demonstrating several new completely game-changing traits. This is different for junior to mid-level where you go from not doing system design at all to doing it and mid-level to senior where you go from a very rough design to one that's incredibly polished.

When it comes to differences, here's a couple that I've seen:

• Staff engineers are thinking more on the 1-2 year time horizon compared to senior engineers who are thinking 6-12 months ahead
• Staff engineers are much more likely to have strong product sense and a clear, defensible roadmap for features. This influences the order in which they design the existing components in the prompt and the future components they think the system will need (which they will design around as they describe how their system is scalable).
• Staff engineers will think outside of technical realm and describe other angles for evolution of the product like logging strategy, experimentation infra, monitoring, and more.

Again, these are more for product engineers, not those who are more on the infra side. Infra is more technically complex, so there's far more scope staying in the technical weeds as opposed to product which is generally regarded to run out of technical scope as you approach L6/Staff.

As a side note, I have generally found that as you get more and more senior, what you do on the job starts converging towards what the interview process looks like, primarily through the behavioral and system design angles. Hiring an L5 or L6 (senior/staff engineer) who can't actually hack it is so, so painful for everyone involved, so interviewers spent a lot of time and mental energy making sure that candidates have genuinely operated at these levels.

This is opposed to L3 and L4 (junior and mid-level) where you go through DSA gauntlets (especially for Big Tech) and you have to fake knowing system design (most L4s don't do system design on the job).

This is why I think it's very valuable, even for folks interviewing, to go through our senior -> staff playlist: [Taro Top 10] Senior Engineer To Staff Engineer (L5 To L6)