Patrick Collison on Stripe’s Early Choices, Smalltalk, and What Comes After Coding

**Patrick Collison** (0:00)
It's interesting to me that we haven't experimented in some sense that much with the paradigm of programming over the past 20 years. You put those together, you now have the ability to, again, at the level of the individual cell, to read, think, and to write. And this starts to really feel like a new kind of Turing loop and to have its own completeness. I think that's a case where the right API design, the right abstraction design ended up having just quite significant business ramifications. I think the basic idea of as development environment and not just text editor is really the right idea. And that's the thing I want to see a return to.

**SPEAKER_2** (0:41)
Patrick Collison wrote his first startup in Smalltalk. Its development environment let him fix errors mid-request, inspect stack frames and resume execution. And he wanted that more than he wanted a mainstream language. He and his brother chose Ruby and MongoDB for Stripe instead. Those decisions still defined the company 15 years and 44 seconds of annual downtime later. Now Stripe is shipping V2 APIs, rewriting core abstractions first designed in 2010 It's taken years. Defining the new APIs is the easy part. Making them work alongside everything already built on the old ones is, as Collison put it, more like an instruction set migration than a product launch. This conversation previously aired on Cursor's podcast also gets into why AI hasn't moved product to V numbers what today's dev environment could steal from Lisp machines and Collison's work at Arc on foundational models for biology. Michael Truell, CEO of Cursor, sits down with Patrick Collison, CEO of Stripe.

**Michael Truell** (1:40)
Well, it's great to have you. Thanks for being here.

**Patrick Collison** (1:42)
Thanks for having me.

**Michael Truell** (1:43)
Great to be here. I've heard that your first start-up was written in Smalltalk. Please explain.

**Patrick Collison** (1:49)
I don't know what there is to explain. It's the best programming language. Well, I had worked on Lisp and Lisp dialects before that.
Actually, I had worked on Lisp web frameworks. And when we went to build our first start-up, we first implemented it in Rails. And then I found, compared to Lisp, that development process kind of frustrating. And we don't need to get into full details, but I thought that continuation-based web frameworks were really the right way to implement web applications. There were no continuation-based framework in Ruby. And I was kind of searching around, I found that there was a good one that had just been written in Smalltalk. And so I decided to play with it a little bit. And then I found that Smalltalk is actually this extremely interesting development environment that had a lot of the aspects of Lisp that I'd really appreciate it there, like a fully interactive environment with a proper debugger, so that you can edit the code while in the middle of some web request or deep in some stack trace or something. And you could, for example, encounter an error with some web request, edit the code to fix the error, and then resume higher up in the stack, such that the entire web request would just complete. And so rather than this kind of annoying feedback loop of having to add some log statements and do this binary search to find the problem, and eventually deploy a fixed version, a process that could take an hour, you could just literally inspect the stack frame, see which variable has the wrong value, fix it, jump back up, hit proceed, and have the whole thing work. So anyway, the point is, in the hunt for this continuation-based web framework, we realized that Smalltalk, in general, had just a much more powerful development environment as compared to Ruby, as compared to basically every other mainstream programming language. And so we decided to use it for the company, which in hindsight was, I mean, I don't know if it was a terrible decision or not. The reason I think one would think it would be terrible is that it would be hard to hire people and hard to scale and whatever. It wasn't hard to hire people, or rather, nobody knew it, but it was easy to teach them. Did they know before they joined? No, no, they learned really quickly. And then you have smart people learn languages really quickly. So I don't think that's really a reason not to use a non-mainstream language. The company didn't work, I think, for unrelated reasons. I think just the idea wasn't that strong. But we also chose Ruby for Stripe, so I don't know, I think maybe the gains were not quite as large as I'd hoped.