Fintech is the industry where every architectural decision compounds into either resilience or regulatory risk. After a decade designing systems that move money, I've learned that the hardest engineering problems aren't the ones that show up in interviews - they're the slow, boring ones around idempotency, reconciliation, and audit. A payment that succeeds twice is worse than one that fails once. Building systems that get this right is what separates fintech teams that scale from those that get stuck firefighting refunds.
My approach starts with the ledger. Before we talk about UI, mobile, or even APIs, I want to know how you model money. Double-entry accounting on top of an append-only event log is the only model I've seen survive contact with auditors, accountants, and angry customers simultaneously. From there, domain-driven service boundaries emerge naturally: payments, KYC, ledger, treasury, reporting. Each service owns its truth, and a robust event bus gives you the eventual consistency you actually need without the distributed-transactions nightmare.
Compliance is not a feature you bolt on at Series B. PCI-DSS scope reduction starts on day one - most teams should never touch a raw PAN, and tokenization through providers like Stripe, Adyen, or Marqeta should be the default. SOC 2 Type II becomes painful only if you wait. I help teams embed compliance into the platform layer so engineers can ship fast without breaking controls. KMS-backed key management, deterministic encryption for searchable PII, and structured audit logs are foundations, not retrofits.
Real-time risk is where AI starts to earn its keep in fintech. Rule engines still catch the obvious patterns, but transformer-based scoring on transaction sequences picks up the subtler ones - synthetic identity, mule networks, account takeover. I've shipped fraud models that run inline at authorization with sub-50ms p99 latency, using a mix of feature stores, vector retrieval, and traditional ML. The trick is building the human-in-the-loop tooling alongside it: analysts need explainable signals, not opaque scores.
If you're early stage, I act as a fractional technical partner - helping you make foundational decisions you can't easily reverse. If you're scaling, my work spans architecture reviews, modernization, and team coaching. Either way, the bar is the same: ship safely, sleep well, and keep the regulators happy. See how I think about fintech architecture or book a call if you want to dig in.