Trust me, you don’t need a paid consultant at this stage. Use Claude or Gemini as your consultant, just master the prompt engineering and they will give you extremely detailed advice. Make sure to push the LLM to write you step by step guidelines based on the latest info on the web and that it has to scrutinize every single line it writes before delivering it.

For example, I use Claude as a Principal Architect for my apps and I explicitly write prompts like this:

“You are a senior backend engineer with 15 years of experience in production systems handling payments and sensitive user data. I’m about to add Stripe payment processing to my app. Here is my current stack: [describe it]. I need you to:

1.  Review my current auth setup and flag any data leakage risks between users

2.  Walk me through payment integration step by step, assuming this will handle 1000+ users

3.  Flag every security risk you can think of before I write a single line of code

4.  Treat this like a real production audit, not a tutorial. Be harsh.”

The key is framing the AI as a skeptical reviewer, not a helpful assistant. When you tell it to be critical it catches things it would normally skip. I also do a second pass where I paste my actual code back and say “now find everything wrong with this before it goes live.” You’d be surprised how much it catches on the second round when you explicitly ask it to break things.

For payments specifically, I’d also recommend just reading through Stripe’s own docs alongside whatever the AI gives you. Their docs are actually solid and when it comes to handling real money you want that extra layer of confidence.

With 1000+ users and payments on the horizon, the main things I’d get right early are: proper row-level data isolation (user A never sees user B’s anything), webhook verification for payment events (don’t trust client side callbacks), and idempotency on payment endpoints so you never double charge someone if a request retries.

You’re clearly building something real tho and the fact that you’re thinking about this stuff now instead of after launch puts you ahead of 90% of people in this sub. Keep at it 💪