Engineering Research
Exploring the architecture behind modern payment systems.
Payment infrastructure is fragmented, underdocumented, and harder to build correctly than almost any other domain in software. These articles document the structural problems — and what better architecture could look like.
Farnaz Bagheri · Software Engineer · Payment Infrastructure
Research Areas
POS System Integrations
How payment terminals communicate with backend services, EMV certification constraints, and the gap between SDK documentation and production behavior.
Processor Interoperability
Why payment processors expose inconsistent APIs for identical operations, and what a normalized abstraction layer would need to handle.
Transaction State Architecture
Modeling payment lifecycle as a state machine — from authorization to capture, void, and refund — across distributed, sometimes-offline systems.
Recent Writing
All articles →A State Machine Approach to Reliable Payment Processing in POS Systems
A research-style treatment of transaction state modeling for POS payment systems, defining an explicit lifecycle, transition constraints, idempotency discipline, and recovery behavior under the failure modes that dominate production — timeouts, duplicate responses, post-capture declines, and partial persistence failures.
What I'd Build Differently: Lessons from Years of Payment Infrastructure
Twenty-seven articles into this series, and the pattern is clear: payment systems fail in predictable ways, and most of those failures trace back to architectural decisions made early. If I could start over with what I know now, here's what I'd do differently — and what I'd keep the same.
Real-Time Settlement vs. Batch Processing: Choosing the Right Model
Every vendor selling real-time payments will tell you batch is dead. It isn't. The choice between real-time and batch settlement is one of the most consequential payment architecture decisions, and it's almost always made for the wrong reasons.
Embedded Payments: Why Every SaaS Platform Wants to Be a Payments Company
Look at any vertical SaaS company's earnings call lately and you'll hear the same word: payments. Toast, Mindbody, Square, ServiceTitan — they all want to be payments companies now. Some are right to want it. Most underestimate what it actually takes.
About
Software engineer focused on payment infrastructure — the backend architecture, device protocols, and integration patterns that underlie POS systems and fintech platforms. Writing toward a more coherent understanding of how payment systems should be designed.
More about me →- Stack
- Node.js · TypeScript · React · MongoDB
- Domain
- Payment Infrastructure · POS Systems
- Protocols
- EMV · ISO 8583 · REST