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Presentation: Architecting a Modern Financial Institution

Track: Architectures You've Always Wondered About

Location: Ballroom A

Day of week: Monday

Slides: Download Slides

Level: Intermediate

Persona: Architect, Chaos/Resiliency/SRE, Technical Engineering Manager


Ever wonder what it would take to rewrite your local bank? With open source, microservices, functional programming (Clojure, Scala), and continuous delivery, right? That's what Nubank did in Brazil, starting with a modern credit card architecture built from scratch, and continuing on to familiar concepts in checking, savings, mobile payments, and beyond. We'd like to walk the audience through the the key elements that make Nubank tick for millions of customers every day, including transaction authorization, messaging infrastructure (Kafka), real time double entry accounting (Datomic), customer and temporal sharding, our analytical environment and the role of predictive models, and some key security decisions we made along the way. You can expect a menagerie of distributed systems, bizarre third party integrations, and humbling lessons learned that may help to explain why bigger banks tend not to attempt this sort of bleeding edge rewrite.


What is the focus of your work today?


I am the co-founder and CTO of Nubank which is a tech company competing with traditional banks. We're based in São Paulo, Brazil and have over 2.5 million customers using our credit card product. We’ve also recently launched a checking/savings/digital payments account to address a much larger market.


What’s the motivation for this talk?


Nubank has focused on functional programming from the very beginning of the company, and we’ve emphasized immutability and simplicity (all the way to the database). Our stack includes Clojure, Datomic, and Kafka (fairly bleeding edge stuff in 2013), and at over 100 engineers and millions of customers, we’ve enjoyed seeing this architecture scale nicely in a complex domain. I think there are some interesting learnings in terms of how the architecture has emerged under these circumstances.

I also think it is interesting that we are building a bank versus any other sort of technology company. While many aspects of building technology remain the same, there are interesting architecture and cultural implications driven by being responsible for money, being regulated, and being required to interoperate with predominantly legacy companies and technologies at the borders. I think there are some some hard-won insights to share, and hope this will be an interesting talk for the audience.


How you you describe the persona and level of the target audience?


This talk is primarily targeted at working engineers who are designing, building, and scaling services in production. For those thinking about scalability, architecture tradeoffs, and service boundaries.

I think the talk will also be interesting for those who are curious about the inner workings of core banking and credit card systems (as opposed to e-commerce or something like that), including relevant differences driven by working in a highly regulated industry.


What do you want “that” persona to walk away from your talk knowing that they might not have known 50 minutes before?


A lot of people dabble in functional programming (and languages like Clojure) in an academic setting and for side projects, but it’s a bit less common to see these patterns in production at scale. I think that's pretty interesting. I hope people take away from it that these design principles aren’t just for academics and weird guys. I also hope that some of the decisions we’ve made and our resulting experience will provide some interesting points of reference for audience members to take back to their day jobs.


What technology problem keeps you up at night?


My largest concern at the moment is as much social as it is technical: the scalability of our interface with our customers (or “operations” in the financial services industry). Unlike Google (who can make it difficult for their customers to reach them), we have a regulatory and fiduciary responsibility to answer the questions we receive. From a customer perspective, it's your money, and it’s important. So I think a lot about how we can maintain a phenomenal customer experience while leveraging technology in the right way so that we scale efficiently (especially from a cultural perspective).

Speaker: Edward Wible

Founder & CTO @Nubank

Edward Wible is Nubank’s cofounder and CTO, responsible for the company’s technology development and infrastructure. Wible is an American who started his career in consulting at Boston Consulting Group (BCG) and in his over 10 years experience he specialized in investments focused on US tech companies. He graduated in Computer Science from Princeton University, with an MBA from Insead.

Find Edward Wible at

Speaker: Rafael Ferreira

Senior Software Engineer @Nubank

Lead software engineer in Nubank from the outset of the company, has taken part in shaping the overall software architecture and engineering organization. Experienced in microservices since before they were called that, built useful systems using RESTful principles and messaging-centric architectures.

Find Rafael Ferreira at

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