Leveraging Spaced Repetition to Power My Weekly Newsletter

The Payments Engineer Playbook, April Cools edition

Some people enjoy magic tricks without ever wanting to know how they work. They are my polar opposites.

I sure hope they’re yours too. We’re cut from the same cloth if you believe that there’s too much “just works” and “off the shelf” in the world. We’re kindred spirits if you tinker, disassemble, and probe.

We’re two of a kind if you always want to learn more.

Today is April Cools: a celebration of what doesn’t fit the mold. This article won’t be my usual thing, and not only because it’s not Wednesday. Today, 1st of April, 2025, I’m putting my obsession with payments technology aside for one week, to shed some light into the making of The Payments Engineer Playbook.

A small but enduring portion of the feedback I get from readers revolves around, not the content of the newsletter per se, but the process of writing it. “How do you come up with enough ideas to maintain the weekly cadence?”, or “How can you find the time to write and edit every article?”.

I’m far from an expert in the topic of writing. I don’t see myself as a writer—finding the right turn of phrase is as elusive to me as it is to you. What I am is a good learner. A great one, if I may be so bold.

That’s because I use a fairly simple tool, in a fairly unconventional way.

Such a tool, and a deeply ingrained habit, is what makes this newsletter possible.

In today’s free article, my very first April Cools, how I leverage spaced repetition to power this newsletter.

Let’s dive in.

The buildup of intuition

I used to play chess when I was a kid.

Not great, and by no means competitive chess. I just enjoyed the occasional game against a friend, or some schoolmate. Sometimes, I won; often, I didn’t.

And like hundreds of thousands of people, in 2021, stuck at home, having watched The Queen’s Gambit, I decided to pick up chess, this time for real.

How original.

Back then, I came across an article titled How To Learn Chess As An Adult, where I was first introduced to Anki, by way of something called The Woodpecker Method.

The basic premise behind that method is that the time constraints in chess forces you to make decisions on the verge of intuition. When you have 3 minutes to play the whole game, chess is less of a thinking game and more of a “feeling”.

If chess is a game of intuitive moves, the Woodpecker Method is the system to build such an intuition. And it’s done by doing the same chess problems, again and again, in shorter amounts of time.

My process was this: using Anki, a spaced repetition tool, I built up a treasure of digital “flashcards” with questions and answers. And, every day, I tested myself, at varying frequencies (less often if I was right, more often if I was wrong), on those questions.

I’m no Grand Master, but I can attest to it. The intuitive recognition of patterns can be developed in a systematic way.

It’s hard for me to put into words what “chess intuition” means. Perhaps the best way to describe it is that now I hear a “voice” in my head telling me what the solution is¹. I can “feel” when it’s the best moment to castle, I can “taste” the beginnings of a tactic. I can “smell” a knight in the outpost.

Of course, I still blunder a lot. But much less than I used to.

Making Memory a Choice

My pivotal moment in the last 5 years has been to realize that The Woodpecker Method can be applied to things other than chess.

As my obsession with chess was dying down, I decided, why not, to add a few cards on the contents of the handbook that I was using to get my AWS Certified Developer.

Two months later, I was passing the exam with flying colors.

Then, I added flashcards to get my boat license.

Again, a breeze.

I used to hate memorizing stuff for an exam. Armed with this Anki tool, I could now remember a huge chunk of what I read, what I watch, what I hear.

Forget Roam, Obsidian and Zettlekasten.

Every note is now written down in my brain.

Let’s get you started

In the last 5 years, I’ve used Anki to learn:

• English vocabulary (by far, the most common usage of Anki)

• Facts about people in my inner circle (birthdays, mostly)

• Conference talks (I don’t use notes when I’m in front of an audience)

• Programming languages’ syntax and their standard libraries

• Large codebases where I needed to hit the ground running

• Emergency drills and on-call playbooks

• Mental math

• How to touch type, and the Vim key bindings

Did I persuade you to give it a go? Now it’s time to talk you out of it.

You see, Anki is probably one of the most intimidating tools to get started. It is as powerful as you can make it be, and overwhelming for the beginner.

That’s why most people end up abandoning: they go to one of those websites selling (or giving away) decks of flashcards, find themselves unable to memorize countries and their capitals, and fail to build the habit.

But if you manage to keep at it, even 15 minutes a day, the results are impressive very quickly.

Every article in The Payments Engineer Playbook is based upon a few sources for which I’ve created at least 50 cards, sometimes even 100. In time, I’ve accumulated close to 3,000 cards exclusively as a result of doing research for this newsletter.

That’s the kind of knowledge that compounds.

So, to wrap it up, let me share with you a few great articles on how to get started, and a few tips from my personal experience.

Sources

First, why books don’t work. If I haven’t persuaded you yet that your reading is ineffective, that article will. Then, the canonical “intro to Anki” is Augmenting Long-term Memory by Michael Nielsen. He and Andy Matuschak (the author of the first article) developed a website called Quantum Country, dedicated to use the ideas of spaced repetition to help you learn quantum computing.

Up until they arrived into the scene, Anki was used merely as a tool for learning new languages (spaced repetition is at the core of Duolingo). Nielsen and Matuschak realized that spaced repetition systems can be used even for mathematics.

However, if you go on Youtube, most advice on how to use Anki effectively is crap. Notice how Nielsen makes the process of creating flashcards as creative as the studying of the material:

I can’t emphasize enough the value of finding multiple different ways of thinking about the “same” mathematical ideas. Here’s a couple more related restatements:

Q: What’s a geometric interpretation of the diagonal entries in the matrix MM†MM†?

A: The lengths squared of the respective rows.

Q: What’s a geometric interpretation of the diagonal entries in the matrix M†MM†M?

A: The lengths squared of the respective columns.

Q: What do the diagonal elements of the normalcy condition MM†=M†MMM†=M†M mean geometrically?

A: The corresponding row and column lengths are the same.

— Using spaced repetition systems to see through a piece of mathematics, Michael Nielsen

You should do the same: figure out ways to create cards in an iterative manner, rather than copying and pasting what’s written in the source. On that topic, Fernando Borretti has a great article on how to write Anki flashcards effectively, and the tricks he provides have a similar sentiment on figuring out multiple perspectives of the same idea:

Cards should be short. They should refer to as little information as possible. They should be like chemical bonds, linking individual atoms of knowledge.

This is the most important thing. By far the worst failure mode is to put too much in a flashcard.

— Effective Spaced Repetition, Fernando Borretti

Chris from Entropic Thoughts has two articles on his personal experience with spaced repetition as well: Early Adventures in Spaced Repetition and Reading Slightly More Incrementally.

And finally, if you want to learn even more, Gwern has put together the most thorough list of resources on spaced repetition you’ll ever see.

Parting List of Tips

I’ve developed a few tricks over the years too! Here are the most relevant:

• Don’t ask “how” questions: “How” is the most ambiguous way to frame a question. Include the proper preposition in the question itself (i.e., “with what…?”, “by doing what?”) so that the answer gets simpler.

• Use mnemonic tricks, and add flashcards for them too. It is easier to remember the differences between RPC and function calls (Reliability, Timeouts, Idempotency, Latency, References²) if you notice that together they form the word ReTaILeR. Tricks like these can be spiced up with a little bit of AI and some creativity.

• Write the shortest question to get a single-word answer: Aim to write, not one complete flashcard, but as many tiny cards as you can. Treat the ideas in the source you want to remember as a complex lattice, with the questions as the links among ideas. This helps separate and schedule differently the concepts that are harder from those that are easier.

• Related to the previous one, write more cards than it feels natural. It doesn’t have to happen on the first pass, but rather, read the source a few times in the span of a few days, adding multiple cards at each pass.

Augmenting Grit Intelligence (AGI)

I want to be the world’s expert at my particular corner of the Internet. And I’m willing to put the time and the effort to become precisely that.

While others are letting machines do the thinking for them, I’m developing a system for generating ideas that’s more traditional.

A First Brain.

This has been April Cools’ edition of The Payments Engineer Playbook. See you next week.

1. Years later, I read Julian Jayne’s The Origin of Consciousness in the Breakdown of the Bicameral Mind, and it resonated A LOT with this.

2. From Designing Data-Intensive Applications, Chapter 4, section titled “The problems with remote procedure calls (RPCs)”.