Chapter VIII
Journal · 73 entries

Paymentsengineeringnotes.

Guides and analysis on Open Banking, instant payment rails, stablecoin infrastructure, agentic payments and Rust, written from inside the systems rather than from the press releases.

Latest · 28 Sept 2026 · 11 min read

Card Auth Expiry: Visa vs Mastercard Capture Rules

How long a card authorisation lasts: Visa's 5/10/30-day rules, Mastercard pre-auth vs final auth, and the capture windows Stripe, Adyen and Braintree use.

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UK rails

Open Banking, VRP and UK payment regulation

Variable Recurring Payments, Verification of Payee, CASS 15 safeguarding and the FCA rulebook, from the API fields down. Start with the VRP guide if you are building recurring account-to-account payments in the UK.

All 9 entries

Standards

ISO 20022, FedNow and instant payment rails

What the message standards and instant rails actually expose to an integrator: FedNow with no payment endpoint, the ISO 20022 structured address rules, and where Swift is taking cross-border settlement.

All 35 entries

Stablecoins

Stablecoin and crypto payment infrastructure

Off-ramps, settlement, developer tooling and the regulatory perimeter in the UK and EU. The two guides cover crypto-to-fiat infrastructure and the tools worth building on; the rest tracks what Mastercard, Stripe and the issuers are shipping.

All 26 entries

Agents

AI agents and agentic payments

The protocols agents actually pay with: x402, Google AP2, Circle Agent Stack, MCP and the issuer-side consent models coming out of India and the UK. Comparisons, not press releases.

All 26 entries

Engineering

Rust and backend engineering for payments

Why payment infrastructure keeps landing on Rust, what UK fintechs hire for, and the supply-chain and tooling incidents that matter if your build touches money.

All 8 entries

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