Architecting a Modern Financial Institution with Vitor Olivier, Thoughts on Immutability, CI/CD, FP

| Podcast with Vitor Olivier Follow 4 Followers by Wesley Reisz Follow 17 Followers on Jan 12, 2018 |

This week’s podcast features a chat with Vitor Olivier. Olivier is a partner at NuBank (a technology-centric bank in Brazil). This podcast hits on topics from several of Nubank’s recent QCon talks and includes things like: Nubank’s stack, functional programming, event sourcing, defining service boundaries, recommendations on reasoning about services, tips (or tweaks) on the second iteration of their initial architecture and more.

Key Takeaways

  • Property-based testing and Schemas (or Clojure.Spec) are complementary.
  • Clojure’s functional nature and Datomic’s features are a match for Nubank’s requirements.
  • A (micro)service needs to be able to create the full representation of the core feature it’s handling.
  • GraphQL is useful to abstract away the distributed system complexity from the mobile (or frontend) developers.
  • NuBank’s uses a combination of monitoring and sanity checks in real time at various levels to keep systems consistent. Once an invariant is broken, the system will try to fix it automatically.
  • Event sourcing architecture offers time-series debugging and improves confidence in the system.

Show Notes

  • 1:24 - What is Nubank?
  • 2:32 - Compete by continuously improving the product.
  • 4:15 - Functional programming a good fit for banking logic.
  • 5:30 - Datomic as persistence layer.
  • 8:03 - Consistency considerations.
  • 9:17 - Accounting view of the world. Maintaining consistency between Nubank’s microservices through monitoring and sanity checks in real time at various levels.
  • 14:30 - Functions get applied to incoming events, stored in temporary version of database; perform sanity checks. If sanity checks pass, the changes are committed, if not, check which invariants are broken and try to fix automatically.
  • 16:12 - Property-based (or generative) testing to find corner cases. Schemas exist for various types and can be used to generate tests.
  • 19:12 - Why use Clojure? Because of Datomic. Clojure makes imperative code look bad; it's useful to stick to functional practices.
  • 21:08 - The Nubank team.
  • 25:14 - Lessons learned building microservices, both building services that did either too much or services that could have been combined into one.
  • 27:18 - How to choose boundaries for microservices. A service needs to be able to create the full representation of the core feature it’s handling.
  • 34:39 - How Nubank uses GraphQL. Abstracts away the distributed system complexity from the mobile developers.


About QCon

QCon is a practitioner-driven conference designed for technical team leads, architects, and project managers who influence software innovation in their teams. QCon takes place 7 times per year in London, New York, San Francisco, Sao Paolo, Beijing & Shanghai. QCon San Francisco is at its 12th Edition and will take place Nov 5-9, 2018. 140+ expert practitioner speakers, 1300+ attendees and 18 tracks will cover topics driving the evolution of software development today. Visit to get more details.

More about our podcasts

You can keep up-to-date with the podcasts via our RSS feed, and they are available via SoundCloud and iTunes.  From this page you also have access to our recorded show notes.  They all have clickable links that will take you directly to that part of the audio.

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