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.
Authorization economics: scheme fees decoded
The interchange bill is the visible part. What actually shows up on the underlying scheme fee statement is where the interesting rebalancing is happening.
Tool-calling for merchant support agents
Merchant support workflows involve looking things up, running checks, and drafting responses. Tool-calling turns an LLM into a first-line agent for well-shaped tasks.
On-chain reversibility: refunds without chargebacks
The absence of chargebacks is a feature and a gap. Design patterns for merchant refund flows in a rail with no consumer dispute mechanism.
Insider threat models for payment platforms
The insider threat model is different from the external one. Where the discipline usually breaks down.
Database sharding for authorization pipelines
Sharding a database is often the wrong first move. When it isn't, the choice of shard key is the decision you can't undo.
When to say no to a customer commitment
Saying yes is easier in the moment. Learning to say no well is one of the highest-leverage skills for engineering leaders.
Terminal firmware upgrades: the field replacement problem
Pushing firmware to a fleet is easy in a lab and hard in the field. What actually goes wrong at scale.
Why cash-out still matters in emerging markets
The digital payments story misses the operator on the corner. Some design considerations for cash-out that don't come up in western integrations.
Travel rule compliance for VASPs
The FATF Travel Rule requires VASPs to share originator and beneficiary information on transfers. Two years in, the compliance patterns are converging.
The prompt injection surface in commerce
Anywhere a merchant or customer supplies input that reaches an LLM, prompt injection is a live threat. A field taxonomy of the attack surface.