Where billing gets risky
The first successful payment is usually the easy part. The harder part is everything around it: duplicate deliveries, delayed events, retries, and product state drifting because handlers are not strict enough.
What I look for
Billing webhook code should make replay safety obvious:
- idempotent writes,
- event logs,
- stable identifiers,
- and narrow transitions for subscription state.
Why this matters
When money is involved, hidden ambiguity is expensive. Replay discipline is one of the clearest signs that a product is built to survive real traffic instead of only demo traffic.
Portfolio signal
I want SaaS repos in the portfolio to show that billing is not just an integration. It is an operational boundary that needs boring, careful handling.