Tag: #payments
Writing on GPUs, LLMs, MLOps, Kubernetes — and mindset · 9 posts
Payment Systems 101: Flow, PSPs, Card Networks, Settlement
What actually happens when you press the pay button, from an engineer's point of view. The difference between authorization, capture, and settlement; the five players (merchant, PSP/gateway, acquirer, card network, issue
2026-07-03 · 13 min read #payments#fintech#systemsPayment Idempotency: Preventing Double Charges
The network will eventually drop, and when it drops, clients retry. But in payments, a retry can become a double charge. Idempotency keys, dedup windows, unique constraints, the retry-plus-timeout problem, at-least-once
2026-07-02 · 14 min read #payments#idempotency#reliabilityDesigning an Invoicing and Billing System — So the Money Does Not Leak
A design-oriented walkthrough of a billing system, from invoice components to billing types, taxes, status flow, data model, payment integration and reconciliation, idempotency, multi-country and multi-currency handling,
2026-07-01 · 20 min read #invoice#billing#system-design#payments#accountingDouble-Entry Ledgers: Designing Systems That Never Lose Money
Why a 600-year-old accounting technique is the beating heart of modern payment systems. Debits equal credits, immutable append-only entries, accounts and balances, the answer to "why not just a balance column?", reconcil
2026-07-01 · 15 min read #payments#ledger#accounting#databasesStablecoins and Regulation — The Rise of the Digital Dollar
A balanced look at fiat-backed versus algorithmic stablecoin structures, the reported 1.2 trillion dollar market outlook for 2028, and the regulatory landscape spanning the U.S. GENIUS framework, EU MiCA, and Korean poli
2026-06-18 · 19 min read #stablecoins#regulation#digital-dollar#crypto#paymentsISO 20022 and SWIFT — The Great Migration of Financial Messaging Standards
From telex to SWIFT MT to ISO 20022 MX — the history and structure of financial messaging. We cover the pacs/pain/camt message families, field mapping between MT103 and pacs.008, the CBPR+ migration, message transformati
2026-06-13 · 15 min read #iso20022#swift#payments#financial-messaging#xmlPayment Infrastructure 2026 — From Visa, Mastercard, Stripe, Adyen, and PayPal to Toss Pay, Naver Pay, Kakao Pay, PayPay, LINE Pay, and Rakuten Pay (A Deep Dive into Global, Korean, and Japanese Payment Networks)
Payment infrastructure in 2026 is no longer the story of "a single card." Stripe and Adyen, perched atop the two enormous 4-party networks of Visa and Mastercard, each push $1T+ TPV; the US, EU, and Asia run on different
2026-05-25 · 33 min read #payments#visa-network#mastercard-banknet#amex#unionpayPayment APIs & Developer Fintech 2026 — Stripe / Adyen / Toss Payments / PortOne / Square / Mollie / Lago Deep Dive
A comprehensive 2026 snapshot of the global, Korean, and Japanese payment API ecosystem. Stripe (still the leader), Adyen (European enterprise), Toss Payments / PortOne / KCP / Inicis (Korea), Square / Cash App, Razorpay
2026-05-16 · 23 min read #payments#fintech#stripe#adyen#toss-paymentsPayment Infrastructure for Solo Developers and Micro-SaaS in 2026 — Stripe, Lemon Squeezy, Polar, Paddle, Creem Deep Dive
Payment infrastructure is the single variable that decides whether a solo developer spends a weekend on billing or three months. Build freely on Stripe, or pay 5% extra to a Merchant of Record (MoR) and offload tax, VAT,
2026-05-14 · 28 min read #payments#stripe#lemon-squeezy#polar#paddle