- If this is a new start up and you're just trying to get product market fit, then you don't need to spend time on making your systems stable to be able to support a big customer. First, you have to do whatever it takes to get a customer, and then a big customer. Plenty of really successful startups have ridiculously messy code under the hood, and that's OK because the job isn't to write clean code, the job is to create product that people love.
- If you are the CTO of this company, then it is your job to figure out what can be done under what time frames, and despite your cofounder needing more features, it is your responsibility to deliver them. Therefore, your cofounder needs to understand this, but since they are non-technical, they probably have no idea. This is on them to educate themselves, but you can help them. Of course, it is also on you to have a backbone and be able to tell your co-founder "No." It sucks, it doesn't feel good, but if you want to be a CTO, then being able to communicate is part of your job.
- What is your assessment and how you are doing financially with your customers? It sounds like your cofounder realized that you haven't achieved a product market fit yet, and they are trying new features to find what resonates with the customer the most. That is a good approach, but even better approach is to figure out what your customer needs before you build any of those features. It's hard to say exactly how to do given that we don't know anything about your application, but people who have figured out how to do it achieve great success. See my notes on [how Rahul started Superhuman](https://smashnotes.com/p/acquired/e/superhuman-with-ceo-rahu...), or how [Ramon made millions with a cheesy blog](https://smashnotes.com/p/my-first-million/e/blogging-his-way...). Those are just a couple of examples that come to mind immediately.
- Lastly, if your cofounder is asking for more features with little results, they are simply insecure and scared the company is about to fail, but instead of admitting what's happening to you and the team, they are hoping to find a way out of this before the collapse. They should talk to other "managers" in the company and find a way together, but they are scared, they are just a little mouse stuck in a dark-dark corner. If that's the case, see if you can figure out how to help them out, if it's possible.
Good luck!