The Payments Engineer Playbook

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The American Way of Building 3DS
3DS is the great equalizer for online payments. But in the US, it is not mandatory. This has more significance than you might expect for engineers.
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Alvaro Duran
How to design mixed payment methods with store credits
Scaling a convenient alternative to cash refunds sows the seeds for a multi-method payment system, and a sophisticated loyalty program
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Alvaro Duran
6
The Payments Engineer Playbook Is Going Paid in 2025—Here's What You Need to Know
Level up your expertise in payments systems and support the ongoing publication of this newsletter.
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Alvaro Duran

September 2024

Why Payments Engineers Should Avoid State Machines
Event-driven money software is replayable and pull-based. Why are state machines still prevalent in payments?
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Alvaro Duran
1
An Approach To Ledgers That Makes Multi-Currency Not Just Possible, But Easy
Or "How To Embed Everything Into Finance"
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Alvaro Duran
1
Engineers Do Not Get To Make Startup Mistakes When They Build Ledgers
Practical accounting for fintech engineers, and also how not to repeat my silly mistakes.
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Alvaro Duran
4
The Most Important Book In Payments Is a Data Systems Book
Challenging the belief that good software design isolates business concerns on the domain layer.
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Alvaro Duran

August 2024

Boring Is Good: How Shopify Prepares for Black Friday
“Today’s Black Friday is tomorrow’s base load” attitude has powered the evolution of Shopify's multi-tenant data architecture.
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Alvaro Duran
How To Scale Payment Systems With The Saga Pattern
What a database paper can teach us about scaling payment systems beyond a single relational database
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Alvaro Duran
4
Exactly-Once Payments At Airbnb
Eventually consistent databases make it really hard to ensure that payments are made only once. Idempotency and clever retries make it possible.
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Alvaro Duran
2
Cringey, But True: How Uber Tests Payments In Production
Well-run payment systems are developed by engineers who understand what is the best use of their time: to catch unknown unknowns, and to do it fast.
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Alvaro Duran
36

July 2024

Stripe Made The Obvious Choice When Building Its Payments API. It Took Two Years To Fix It.
Going from a single Charge object to represent a payment to a dual PaymentIntent/PaymentMethod was a feat of engineering, and a lesson on how to be…
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Alvaro Duran
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