Scale is Overrated in Payments. You Should Focus on Scalability Instead.

Black Friday And Making Payment Systems Scale

This is a bit weird to admit, but when I speak at conferences, I am terrified.

My most reliable tool for managing this anxiety has been to be over prepared. When I’m onstage, I have a script in front of me that I deviate very little from.

I know when to click the next slide, when to raise my voice, when to pause for dramatic effect.

I try to leave very little to chance, so that I can play offense.

But Q&A sessions can’t be planned. Q&As are about playing defense.

Some speakers ask organizers not to allow questions at the end. I think that is a mistake. Very often, these questions are what little speakers can get in the form of honest feedback.

That’s why I put myself through them, despite the anxiety and terror. Q&As are a chance to learn.

This is exactly what happened when I spoke at Pycon SK two weeks ago, delivering Pyments: How to Design Payment Applications in Python.

Someone asked some version of this: Does this design scale during Black Friday?

This is an important question. Black Friday is one of the most important shopping events of the year. A payments application that malfunctions during Black Friday is very harmful to the company. Payments must always work, especially when it’s table stakes.

However, scale has nothing to do with Black Friday. Scale is in fact irrelevant when it comes to payments.

I don’t think that is controversial. Rather than scale, engineers building payment applications should focus on scalability: being able to add capacity on demand, rather than predicting the capacity that will be needed.

Designing for scale is not the same as designing for scalability.