Notes

Notes from the work.

Technical write-ups from building trading platforms, payment systems and products. Each one says whether it comes from production or is a design proposal.

11 Nov 20269 min readFrom production workMT5 Manager API vs Web API: which one should your back office use?MT5 Manager API or Web API for your back office: a practical comparison of latency, writes, deployment and failure modes, from running both in production.
11 Nov 202610 min readDesign proposalCrediting a payment to an MT5 balance exactly once: claim, act, resolve, reconcileHow to turn a payment webhook into one MT5 balance operation: unique event keys, an atomic claim, a reference in the deal comment and daily reconciliation.
11 Nov 202610 min readDesign proposalDesigning an MT5 investor portal with wallets and IB commissions: the five questions that decide the buildFive questions that decide the cost and risk of an MT5 investor portal with wallets and IB commissions, and the architecture I would build on the answers.
11 Nov 202610 min readDesign proposalHow I would architect a proprietary B-Book trading platformA design proposal for a broker-owned B-Book execution core: the components, five design rules, failure scenarios, recovery and what a first sprint must prove.
11 Nov 20269 min readDesign proposalDouble-entry ledger design for fintech startups: the smallest version that is still correctA minimal double-entry ledger in PostgreSQL for wallets and stored value: three tables, one posting path, safe withdrawals and daily reconciliation.
11 Nov 202610 min readFrom production workWhat founders should look for in their first fintech engineerEight things a founder can check in a first fintech engineer without reading code, plus first-call questions, good and worrying answers, and red flags.
4 Oct 20264 min readFrom production workBuilding on the MetaTrader 5 Manager API: five lessons from a real-time risk monitorWhat I learned building a C#/.NET service on MetaQuotes' MT5 Manager API for a prop-trading platform: pumping, thread safety, verification and safe deploys.
4 Oct 20264 min readFrom production workPayment webhooks that never double-credit: signatures, idempotency and reconciliationA practical checklist for card, wallet and bank payment callbacks: verify signatures, process each event once, survive retries and out-of-order events, and reconcile.
4 Oct 20263 min readFrom production workChanging a message between two services: why the consumer ships firstWhen two services talk through RabbitMQ, a new field can be silently dropped. How to find where it disappears, and the deploy order that keeps both sides working.
4 Oct 20263 min readFrom production workHow I use AI coding assistants without shipping their mistakesAI assistants such as Claude Code and Codex speed up exploration, boilerplate and review. These are the habits that keep their confident mistakes out of production.
4 Oct 20264 min readFrom production workOne app, two app store rulebooks: shipping a Flutter marketplace on Google Play and the App StoreLessons from releasing a Flutter app on Android and iOS: Apple's in-app purchase rules, platform-aware pricing, push notifications, old app versions and deep links.
4 Oct 20264 min readFrom production workHow prop firms enforce daily loss and max loss rules, and why timing mattersA plain explanation of prop-firm challenge rules (profit target, daily loss, max loss, consistency) and what it takes to enforce them in near real time.