Solo dev with a day job: What I learned wiring Stripe + Google Play billing at 3am

Hey everyone 👋

I'm Usama, a project manager by day and a solo dev by night. For the past few months I've been building EpicNotes — a native notes app with AI cleanup for the "forgotten combo" of Android phone + MacBook.

The tech part was hard (Kotlin Multiplatform, Supabase, local-first sync). But the part that broke me was the payment infrastructure.

Here's the 36-hour debug marathon I went through last week:

🔴 Android SDK had a blank API key nobody noticed until I tried a real purchase

🔴 Stripe webhooks had a mismatched signing secret (spent 3 hours thinking my code was broken)

🔴 Out-of-order webhook retries were resurrecting cancelled subscriptions (zombie Pro users!)

🔴 The paywall had a bug where the X button wouldn't close unless the checkout finished — had to kill the app

🔴 The RevenueCat webhook was never wired up, so Android purchases flew into the void

Every single one of these hit me with REAL MONEY on the line. I bought my own subscriptions, refunded them, watched the database rows flip, and debugged at 2am after a full day of meetings.

By the end, I had:

✅ Stripe (Mac) fully certified — purchase, refund, cancel, all automated

✅ Google Play (Android) fully certified — same paths, different rails

✅ Webhooks that check Stripe/RevenueCat's live state instead of trusting event payloads

✅ A paywall that closes when you hit X (revolutionary, I know)

Launching on PH on Oct 6. The app is live on Tiny Startups today if you want to see it.

What I learned:

1. Test with real money. Test mode lies to you in subtle ways.

2. Webhook retries will bite you. Always re-fetch from the source of truth.

3. The "I'll just fix one more thing" trap is real. When it works, ship it.

4. Having a day job is a feature, not a bug — it forces you to be disciplined with your building hours.

Would love to hear from other solo devs: What's the most painful infrastructure you've had to wire yourself? Payment processing? Auth? Something else?

(P.S. If you're building something, I'm happy to return the favor — drop your link and I'll check it out)