Nubank Engineering Meetup #12 offered valuable insights into the company’s technical evolution — how we’ve reshaped our platforms, systems, and career paths over the years. The conversation was led by Bel Gonçalves, now a Principal Engineer at Nubank, who shared the lessons learned over nearly a decade building technology at the company.

More than an inspiring personal story, the meetup gave attendees a deep dive into the topics that shape our daily engineering work — from architectural decisions to the development of large-scale technical career structures.

From a single product to a platform-based architecture

Nubank’s original architecture was simple, like many early-stage startups: built for a single product (credit card) in a single country (Brazil). But as we expanded by adding financial services, entering new markets, and navigating diverse regulations, this structure had to evolve.

The answer was platformization. The challenge was to build systems flexible enough to support different products, across multiple countries, with unique requirements, without rewriting everything from scratch each time. This meant clearly separating product-specific logic such as localized business rules from reusable components such as authorization engines and card and account management.

By making services more parameterizable, we accelerated development, reduced redundancy, and maintained the resilience needed to operate at scale. The journey included tough decisions, such as extracting critical code from legacy services in production, rewriting foundational components, and avoiding overengineering by balancing generality with simplicity.

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Platforms that power scalability

One of the clearest examples of this shift was the creation of the card platform, which decoupled debit and credit functionalities from specific products or geographies. What used to be handled by a single service like the former CreditCardAccounts that as the name suggested, was specific to credit card, was restructured and endup derivating other services more flexible and capable to adapt to different realities, such as Brazil’s combo card and Mexico’s single cards for debit and credit.

Another critical milestone was the evolution of our Authorizer system, responsible for real-time transaction approvals. As one of the most sensitive parts of our operation, its migration from physical data centers to the cloud required low latency and high availability, especially to maintain communication with partners like Mastercard. This project required not only technical excellence but also meticulous planning to avoid any disruption to customers.

Standardization as the backbone of consistent engineering

To support engineering scalability, Nubank adopted a consistent approach rooted in standardization. All teams work with Clojure, build microservices, and favor asynchronous communication. This shared foundation encourages reuse, lowers cognitive load, and enables more predictable architectural evolution.

Our use of both Clojure and the Datomic database, both rooted in functional programming, also reflects a focus on safety and predictability. Immutability, for example, is not just a design choice—it’s a necessity to prevent harmful outcomes from incorrect system states.

This level of consistency helps teams replicate proven patterns and best practices across different contexts, accelerating product and market expansion.

The technical career path at Nubank

As our architecture has matured, so too has our technical career framework. The path includes clear milestones: engineer, senior, lead, staff, senior staff, principal, and finally, distinguished engineer. Each level brings increasing responsibility, not just in code, but in system-wide and strategic influence.

Unlike traditional models that nudge engineers into management roles, Nubank supports the growth of deep technical careers. Engineers can specialize in a given technology or take on broader roles, becoming cross-team technical leaders, especially in products or platforms with many stakeholders.

We also encourage movement between tracks. Experience in people leadership, for instance, can add perspective and empathy to those returning to hands-on technical work, strengthening business understanding and collaboration skills along the way.

Engineering at the intersection of tech, product, and business

In our cross-functional environment, engineering goes far beyond code. Engineers are involved in product decisions, help shape go-to-market strategies, and openly discuss trade-offs with stakeholders from other disciplines. Collaboration with data, design, and business teams is part of our daily rhythm, improving both product quality and creative thinking.

This collaborative model means engineers need not only technical depth, but also strong communication, active listening, and negotiation skills.

Culture, trust, and inclusion as core pillars

The architectural structure of Nubank is not just built on services and platforms — it’s built on people. Teams are the core unit of our company, and collaboration is the most essential skill. Behind every critical system, there’s a trusted network where different voices, backgrounds, and ways of thinking come together.

Building strong and diverse teams is part of our culture — and that’s why it’s a strategic priority for us. In initiatives like the creation of the NuCel team, we actively seek to build teams made up of people with different abilities, experiences, and perspectives across functions like engineering, product, design, and more.

Environments like this lead to more complete, empathetic, and relevant solutions for the people who use our products.

Balance and ownership in a high-complexity environment

With over 100 million customers, a growing product portfolio, and operations in multiple countries, pressure and complexity are part of our daily challenges. To manage this, our engineering team relies on mature processes, transparent communication, and a culture of autonomy with accountability.

Planning cycles balance short- and long-term goals. Product timelines are co-developed with engineering, with technical feasibility, resource constraints, and risk trade-offs always in the equation. It is common to adjust scope or renegotiate deadlines, always with a focus on delivering value sustainably.

A culture anchored in learning

If one principle guides everything we do at Nubank Engineering, it is continuous learning. Whether it is tackling a massive refactor, launching a new platform, or navigating the next career step, the mindset is always to stay curious and stay adaptable.

It is not just about mastering a tech stack or leading high-impact projects. It is about being where innovation happens, even when that means stepping out of your comfort zone.

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