Writing
Notes from systems meeting real devices.
Notes on payment systems, device software, transaction uncertainty, platform design, and the emerging role of AI in commerce. I write from the questions that appear in real operating conditions.
Building a connector abstraction layer
Every payment platform ends up with a connector abstraction. The design choices that make one durable, and the ones that guarantee it will be rewritten in 18 months.
Grounding LLM answers with source citations
For commerce applications, an LLM answer without a citation is not an answer — it's a liability. The engineering pattern that actually works.
SEPA Instant: verification of payee in practice
Verification of payee became mandatory across SEPA in October 2025. The first months in the field show a predictable pattern of edge cases.
PCI-DSS v4.0: what actually changed
PCI-DSS v4.0 is now mandatory. Beyond the well-publicised customized approach, several less-discussed changes shift how integrations should be built.
Compensating for silent quitting
The engineer who is present but disengaged is a specific management problem. What's actually going on, and what a manager can do about it.
MiCA in year two: what changed for issuers
The Markets in Crypto-Assets regulation has been in full effect through 2025. Two years in, the operational patterns are becoming visible.
MPoC (Mobile PIN on COTS): security assumptions and gaps
PCI's MPoC standard formalises PIN entry on off-the-shelf phones. The assumptions worth challenging in an integration review.
Reconciliation as a first-class service
Reconciliation gets treated as a nightly batch afterthought. Elevating it to a first-class service changes what the rest of the platform can guarantee.
The three golden rules of honest financial terminals
Terminal firmware breaks in patterns. Three rules would eliminate about half of the incidents I've been paged for.
FedNow at scale: three years in
The Federal Reserve's instant payment service crossed its third live year in July 2026. Adoption looks different from what the launch materials promised.