Griffin is a banking-as-a-service platform and part of the new wave of API-driven banking. Their services allow Fintech businesses to integrate banking features quickly and securely. In March 2023, Griffin was granted their UK banking license by the Financial Conduct Authority, making them a fully-regulated UK bank.
We caught up with Allen Rohner, Griffin Co-founder and CTO (also Co-founder of CircleCI), to discuss how they’ve built a bank, from the ground up, using Clojure.
Joe: So what does Griffin do?
Allen: We are a fully regulated UK bank. We call it “the bank you can build on”. That means we’re like AWS for banking. So there’s an API to onboard a customer, an API to create a bank account, an API to make a payment.
By law, fintechs must work with a bank to do these things, and right now that means a legacy high street bank with mainframes. Griffin is the bank plus technology platform that all future fintechs would build on.
We got our license in March and we’re still in what’s called ‘mobilization’, which is basically like training wheels. The training wheels come off when we complete an audit, raise some more money, and finish writing the code. That should be Q3 or Q4 this year.
Joe: So presumably, the mission of Griffin would be to disrupt the market, have a more modern set of technologies, a better, faster delivery capability than some of the existing banks?
Allen: Yeah, exactly. We kind of joke that we’re a tech company that happens to have a banking license.
Joe: How did Clojure end up becoming the language of choice for the platform?
Allen: I mean, the flippant answer is: because I liked it. The serious answer is: Clojure is the right choice because it’s immutable, it’s powerful; it’s a good fit for financial services and anything that needs an audit log.
There is a longer story about how I arrived at Clojure. I graduated from college (you UK folks would say ‘university’) in 2005, and I got a boring enterprise software job and, uh, was pretty unhappy with it. Then I started reading Paul Graham, and he was writing about how you should both start a startup and work in Lisp. And so I said, Hey, let’s do both of those. At the time he was saying, don’t use Common Lisp because it’s old, fragmented, and there wasn’t a good implementation that did everything. There was like one implementation that was good at threads and another implementation that was good at, let’s say, graphics. And if you wanted to do graphics and threads, you were outta luck. He was saying, “Wait, wait, I’m gonna work on this”.
The problem with Common Lisp is that it needed a BDFL like Python, and there wasn’t one yet. And so PG was saying, well, “I’ll start Arc”, but he’d been talking about that for multiple years. So then I started writing my own Lisp, got about halfway into it, and then I saw that Rich released Clojure. That was probably 2007 – one of his first announcements.
I looked at Clojure and I said, “Well, that’s way better than what I would’ve written”. So then I did a startup that didn’t go anywhere, and then I founded CircleCI in 2011. This is also getting into the history of Griffin as well. I hired David [Jarvis], my co-founder at Griffin, as engineer number nine or so at CircleCI.
David later went on to work at Standard Treasury, which was a YC company that was trying to sell modern APIs to US banks. That ended up not working out. Too late in Standard Treasury’s runway, they said, “Instead of trying to sell the banks, let’s become a bank”. They figured that out too late. David always liked the idea and he saw Monzo get authorized in 2017. He said, “Well, if Monzo can get authorized for this retail bank, then we can get authorized for this tech infrastructure bank”.
So, by this point, I’d been using Clojure for a decade and it worked great at CircleCI and it was a very good fit for financial services.
Joe: So you were coming to Clojure from a Lisp background. Had you worked with JVM languages before that?
Allen: Not really. I had, maybe, three months of Java before using Clojure. Before that my prior experience was C and C++, Python, and Ruby.
Joe: So did you see the JVM as a benefit or a drawback? People talk about the ‘JVM tax’ (on resources like memory). Were you thinking that way?
Allen: I did at first, but my perspective has changed. For the first couple of years I didn’t appreciate it [the JVM]. But now I’ve seen other niche startup languages try to grow, and they run into the library problems and run into problems making the compiler and the runtime fast. It’s become obvious to me that the JVM is a huge benefit.
Joe: When you were working on CircleCI and also when you were starting Griffin, were you mindful that this choice of language and technology would have an impact? Did you feel that using Clojure said something about the business?
Allen: Yeah, I think it definitely says something about the company, something I thought was good.
If we had picked Python, it’s very boring and reliable, and the same could be said of Java. But you’re picking the lowest common denominator. I would say high performers, and the best programmers are often people that will only work in niche languages.
The problem is, there are good Java programmers, but there are also thousands of terrible Java programmers. If you pick the right niche, it’s easier to find the high-end talent. I think Paul Graham also made a very strong case that in a startup, you should be using the most powerful language you can, and that is Clojure.
FoundationDB
Joe: How would you describe the architecture of the Griffin platform?
Allen: We’re running Clojure on Kubernetes, on AWS, and we are almost entirely event sourcing.
The database is FoundationDB, and this additional proprietary thing that I really need to open source (I ported Datascript to FoundationDB). It’s a Datomic-like layer that writes directly to Foundation. I should talk about Foundation, cause it’s awesome.
FoundationDB is a strict-serializable key value store that supports transactions. It was originally a Silicon Valley startup and then got acquired by Apple in
