There are a LOT of questions in this section. You probably won't have time to get to everything, so I would pick and choose based on what you're most concerned about. Reminder of set-up:

“I’d love to ask (the founders) some questions about the business to better understand how to evaluate my offer, and how I can be valuable to [STARTUP].”

Post-launch, metrics:

These are more sensitive questions, so it’s best asked of founders / leadership team.

• [ ] What key metrics are you tracking around the success of the business? How are you doing on each of them? — this is a soft-ball if you're less comfortable with getting into the numbers; but still recommend digging into metrics below
• [ ] How much revenue are you generating? How much of that is recurring? — compare this to duration of time to assess pace of growth; compare this to valuation to assess if richly valued
• [ ] What’s your growth rate in terms of # (paying) customers? In terms of revenue? How have your growth rates changed in the past 3-6 months? — understand slope of trajectory
• [ ] How much of revenue growth is driven by new customers vs. existing customers paying more? — ideal: mix of both; existing customers paying more is a great sign
• [ ] What channels are your biggest growth drivers? — ideal: organic like word-of-mouth, referrals, SEO; paid channels are ok but need line of sight into how they maintain their edge
• [ ] What does customer retention rate look like? What does dollar retention rate look like? — customer retention rate measures % of customers that stick around; dollar retention rate measures % spend that sticks around; possible to have >100% dollar retention rate through growing spend among active customers
• [ ] Are there specific public companies that you believe you’re comparable to? — get external benchmarks for how big this can be
• [ ] What’s your runway based on current burn? How do you expect that to change in the next 3-6 months? — 2+ years are ideal; burn should be maintained or reduced in bad markets
• [ ] What sort of growth do you need to meet / exceed investor expectations for the next round? — check how far along they are

Strategy / org:

These questions can be asked of the founders or hiring manager — also interesting to ask these of multiple people to see where team is aligned vs. not.

• [ ] How has the economic climate impacted your roadmap? What product areas are you doubling down vs. cutting back from? — check focus and ability to adapt
• [ ] How do you make decisions about what to build? Who calls the final shot? — check if this fits with how you prefer to work
• [ ] Who are your best customers? What have you learned about them? — check that they have a deep understanding of customer needs
• [ ] What are your customers’ biggest objections to adopting / paying for this solution? — any strong product thinker has this top-of-mind
• [ ] What's the plan to 2X, 5X, 10X, 100X from a product / sales & go-to-market perspective? — check their ability to think and execute on the long-term