Payments and subscriptions that hold up
Connect checkout, subscription status, and access to the product. Test renewals, failed payments, and cancellations so you understand what happens after someone pays.
Checkout · Billing · Customer access
1:1 APP & PRODUCT MENTORING
Go beyond
vibe coding.
Your prototype works. Let’s get it ready for paying customers.
You’ve built the first version with Claude, ChatGPT, or another AI tool. Now come payments, subscriptions, customer data, and the confidence to launch. I’m Konstantin Kaufmann. I’ll help you build and understand those parts, while checking that you’re making something people want.
1:1 support on your app. You don’t need an engineering degree.
Nearly a decade in productA dozen product managers trainedBuilding my own SaaS
FROM AI PROTOTYPE TO PRODUCTION
What happens when your app
leaves localhost?
Someone pays. A subscription renews. A customer trusts you with their data. We’ll work on the parts you need to understand and operate when your app starts serving real people.
Customer data with clear boundaries
Decide what data your app needs and who can read or change it. Review account permissions, admin access, backups, and deletion before you invite people in.
Accounts · Permissions · Data handling
A deployment process you can trust
Set up automated tests and a CI/CD pipeline that checks changes before deployment. Know how to investigate a broken release and get back to a working version.
Tests · CI/CD · Recovery
Analytics you and your agents can use
Track the steps that matter, from signup to payment and repeat use. Give your AI agents controlled access to those analytics so you can ask where people get stuck and what they actually use.
Product events · Funnels · Agent access
Automated security and privacy checks
Add checks for exposed secrets, vulnerable dependencies, and unintended access to customer data. Review what you collect and retain, and turn the findings into fixes you understand.
Security checks · Privacy · Review findings
Evidence for what to build next
Use customer interviews and product data to test demand and your assumptions about pricing. Choose a small experiment or release, then use what you learn to decide where to spend your effort.
Validation · Interviews · Product decisions
MEET YOUR MENTOR
I’ve led product teams.
I also build my own app.
At N26 and Urban Sports Club, I worked on payments, infrastructure, and products people used every day. At Kaufmann Health, I built and run the software myself, from product decisions and engineering to deployment and billing.
I like the zero-to-one part: turning an idea into something people can actually use. Building Kaufmann Health taught me a different side of the work I’d spent years leading in product teams.
I’ve also trained a dozen product managers and developed a 12-month product management curriculum as Head of Academy at the Franklin Institute of Applied Sciences. Explaining a decision—and helping someone make the next one themselves—is work I know well.
I studied economics, and I’m comfortable working through business models. In my experience, the harder part is execution: checking what people need, choosing what matters, and getting it built. That’s where we’ll spend our time.
WHAT I’M BUILDING
Kaufmann Health
A SaaS and somatic therapist directory, built with Next.js, Supabase, and Stripe Connect. I run the product myself, from subscriptions and scheduling to deployment.
Visit Kaufmann HealthPRODUCT DISCOVERY BEFORE MORE CODE
“I’d use that”
isn’t validation.
I’m a fan of The Mom Test and Lean Startup. We’ll look at what people already do, test assumptions, and let the answers change the plan. It’s the approach I used to build Kaufmann Health.
Questions worth asking before the next feature
- What happened the last time someone had this problem?
- How do they solve it today—and what does that cost them?
- What is the smallest thing we can build or test to learn more?
For Kaufmann Health, therapist feedback and the economics of the service led me to change from a commission model to SaaS subscriptions. Learning something that changes your plan is progress.
HOW 1:1 MENTORING WORKS
First, we review
the app you’ve built.
We start with the prototype you already have. Together, we identify what needs attention before launch and what can wait. You learn the reasoning as we make changes to the actual app.
- 01
Show me what works—and what worries you
Walk me through your prototype, who it’s for, and what you’re unsure about. We’ll trace a customer’s path through it and agree on the first things to address.
- 02
Review what you’ve built
In our sessions, we review what you’ve learned and built. I’ll explain the tradeoffs, ask difficult questions, and debug the implementation with you.
- 03
Build, test, and come back with evidence
Between sessions, put the decisions into practice. Bring back the code, the interview notes, or the thing that broke. We’ll use that to decide what comes next.
AFTER THE FIRST RELEASE
What should you build
after launch?
We can keep working together as customers start using the app. Their feedback may change your priorities, your pricing, or how you choose to fund the next stage.
Understand what customers do
Use your analytics and customer conversations to see what’s useful, where people leave, and whether the next feature is worth building.
Revisit the business model
Explore pricing, packaging, and the economics of serving your customers. Turn a new assumption into something you can test.
Think through funding options
If funding becomes relevant, we can explore possible routes and what evidence or preparation each would call for. We’ll identify what you would need to demonstrate before deciding where to spend your time.
STARTING & PRICING
Let’s talk about the app
and where you need help.
This is paid 1:1 mentoring. After an intro conversation, I’ll propose what we should work on, how often we should meet, and a price. You’ll have those details before deciding to start.
Tell me about your projectQUESTIONS ABOUT APP MENTORING
Questions about
working together.
I have built a prototype with Claude or ChatGPT. Is this for me?
Yes. This is for founders and people building their own products who have something working locally and need help preparing it for real users. You might be unsure about accepting payments, managing subscriptions, protecting customer data, or deploying changes. Bring what you have built; we will work through those decisions together, while checking whether people want the product.
Do I need a technical background or an engineering degree?
You do not need an engineering degree. You do need time to work on your app and a willingness to learn how it works. Bring your current project and tell me what you have tried. We will work out whether I can help from your starting point.
Can you help with payments, subscriptions, and customer data?
Yes. We can work through checkout, subscription changes and cancellations, failed payments, and rules for who can see or change customer data. We test the important flows in your app before inviting customers, and set up ways to spot problems after launch. Production readiness depends on what your app does and what its users need.
Can I use my AI agents to understand how people use my app?
Yes. We can define the events that matter, such as sign-up, first use, and payment, then set up analytics your agents can query. You should be able to ask where users drop off or whether a change helped, with access controls and limits on which customer data those agents can reach.
How do I know I have not broken something when I deploy?
We can set up automated tests and a deployment workflow that runs them before a release. This is often called CI/CD. We focus on the parts that would hurt your customers if they failed, use a preview environment to check changes, and work out how to recover when a release goes wrong.
Can we automate security and customer data checks?
Yes. We can add checks for exposed secrets, vulnerable dependencies, and whether users can access only the data they should. We also review what customer data you collect, where it goes, and how it is deleted, and add tests for those rules. Automated checks help catch mistakes as you build; they still need review and maintenance.
Which tools and technologies can we work with?
My own app, Kaufmann Health, uses Next.js, Supabase, and Stripe Connect. I also work with AI coding tools and automated workflows. Those are concrete starting points for implementation discussions. If you use a different stack, tell me about it so I can be clear about where my experience is useful.
Can you help me find out whether people actually want my app?
Yes. We can prepare customer interviews, look at how people solve the problem today, and design a small experiment to test demand. I use The Mom Test and Lean Startup to focus on what people do and commit to, rather than compliments about an idea. Validation continues after launch: we use what customers say and what they do in the app to decide what to build next.
Can we also work on the business model or explore funding?
Yes. If those decisions are holding you up, we can work through who pays, what they pay for, pricing assumptions, and the costs of serving them. We can also explore funding routes and the evidence, product milestones, and materials you would need to pursue them. These conversations support the work on your product and its customers.
Will we work on the actual implementation?
Yes. We can review your code, work through architecture, and debug together. The purpose of mentoring is for you to understand the app and keep building it yourself. You bring your project; we work through the decisions and problems in it.
How much does 1:1 mentoring cost?
Pricing depends on the support and session cadence your project needs. Start with an intro conversation or a project inquiry. I will propose a focus, schedule, and price before any paid mentoring starts.
TALK TO ME
Show me your prototype.
Tell me what already works and what you’d want to feel sure about before letting customers use it. I’ll read your message and follow up by email.
Or book an intro callTell me about your project
What works already? What’s keeping you from launching?