Blog & insights.
Writing from our founder, Anselm Fowel — on fintech, engineering leadership, product craft, and building at scale. Articles live on anselmfowel.com and stream in here as they are published.
Why Your Retries Need Idempotency Keys
A few years ago I got paged at 2am because a merchant had been charged three times for the same settlement batch. Not a huge sum, about 4,200 euros total, but...
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The Real Cost of a Bad Hire
A few years ago I signed off on a senior backend hire who interviewed beautifully. Sharp answers, confident on distributed systems, name-dropped the right...
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Building a Feature Store for Fraud Models
The first fraud model I ever put into production was wrong about a third of the time, and it took us two weeks to figure out why. The model was fine. The...
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Building Trust With a Team You Just Inherited
The first team I inherited had already lost two managers in eighteen months, and they told me so in the first meeting. Not as a complaint, exactly. More as a...
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The Anatomy of a Payment Authorization
A customer taps their card at a coffee shop, and roughly 300 milliseconds later a little screen says "Approved." In that blink, a message crossed four or five...
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When to Escalate and When to Absorb
A payments engineer pinged me at 11:40 on a Tuesday night: our settlement reconciliation job had thrown an exception and stopped halfway through a batch of...
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Designing for Chargebacks and Disputes
The first serious chargeback I ever dealt with cost us about £40,000 and, worse, taught the whole company that our dispute process was held together with a...
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The Manager Energy Audit
Last spring I sat down with one of my best engineering managers for what was supposed to be a routine one-on-one, and she spent the first ten minutes...
Read articleHow to Test Code That Talks to a Bank
The first time one of my payment services took real money out of a real account during a test run, I was standing at a whiteboard explaining to a new hire why...
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