Xjyuk

There is a blockchain fintech startup that somehow found my profile and wants to interview me for a senior tech role.

However, I don't understand their business at all, primarily because I don't understand finance and blockchain at all. I have always avoided investing/speculating in bonds, stockmarket, etc. because I'm pretty broke to begin with. I think they would be a huge time sink for no benefit when I don't have leverage. I also have only a very vague idea of blockchain (I have never even read how Ethereum's smart contracts work, for example).

What kinds of questions should I be asking them and myself to consider whether to join that fintech startup or not, assuming I could get an offer?

As other answers have stated, learning the technology isn’t too big a deal; it’ll be like learning any other technology stack.

But while you’re worrying about whether you’re up to the task, remember to do your due diligence in researching whether the “company” itself is up to the task. A “startup” in a buzzwordy field that cold-calls folks without appropriate tech experience in the field makes my spider-sense tingle — how do you know it’s not just two naive knuckleheads living in mom’s basement? Make sure you don’t end up working for free on a project that will never see the light of day.

I co-founded a blockchain company with my friend, without any previous blockchain experience/knowledge, nor investment (I still don't).

But I do know how to write code, how to design a solution on the cloud; most importantly, I can learn a new technology quite quickly - as a modern software engineer, this is pretty much a requirement.

If you can do all these, don't worry about it. Blockchain is pretty easy to learn. Find a good tutorial to follow, craft a few experimental smart contracts and you're good to go - just like learning any other new technology stack.

The number one question you should ask a start-up is how they plan to make money. If you can't figure it out and/or they don't have a plan to get to monetization, that's enough of a red flag to make your decision based wholly on your desired career tracking.

For a tech focused job, you should ask what tools/technology they use and how they plan to place you within their staff. Then compare that with how you want to track your own career.

Finally, compare those two questions and make your decision based on the merits of answering "will they exist long enough for me to move in the direction I want to move?" If the answer is "no," don't consider it.

Immerse yourself in some focused internet searches and read up on the basic foundations of Bitcoin, proof-of-work, blockchain fundamentals, etc... And then after that makes sense read up on derivative works such as Ethereum, et.al. And then go buy a small amount of Bitcoin or Ethereum to try it out and learn how digital wallets work.

If you can follow the high-level math and basic principals of what's explained online - and feel like you would enjoy working this space, then continue on in the interview process. That sort of interview prep will open you up to the most basic and expected questions you can ask back to them, including:

"Can you explain your business model to me?"

Asking that assumes that it's not well defined on their website or has already been stated. If it has, you can ask more specified questions about products, code, customers, reach, etc... Ask how they are going to grow their business from startup to an established firm.

If you like their answers, then it might be worth a shot.

Update - I had a comment under the original question above about avoiding any discussion with this potential employer regarding your financial status. It appears to have been removed. Not sure why, so I'll restate it here: Avoid telling any company involved in finance about your own financial situation ("broke" - your own words). This is probably good advice for any interview, but I had one friend lose his job at a bank for having bad credit. I wouldn't want you to walk into an interview and start off on the wrong foot.

It's not an absolute necessity to understand the business. From the sounds of it, they didn't reach out to you because of your expertise in fintech or blockchain. Do some high level reading up on the company, what they do, what markets they serve and do some high level reading on block chain so that you at least have some idea of the domain in which they operate. If you're interested in either fintech or blockchain then this may be a good opportunity for you to get your feet wet and start gaining some experience and knowledge in both.

If you're offered and if you accept a job then you can dig more deeply into the company, their market, and the technology they use to serve that market. The more you know about these the better you can serve the company in your role.