10 years of engineering at Nubank: Lessons from scaling to 122+ million customers

At the 14th edition of the Nu Engineering Meetup, Lucas Cavalcant, Distinguished Software Engineer and Senior Architect, shared insights from his decade-long journey at Nubank. 

Having joined the company in late 2013 as one of its very first engineers, Lucas has been at the center of every major architectural decision, from the earliest credit card systems to the large-scale infrastructure changes required today to serve over 122 million customers.

Leadership beyond code

For Lucas, reaching senior technical leadership is about much more than technical skill. Whether leading a project, a team, or a specific technology area, influence comes from the ability to communicate ideas clearly, bring people along, and guide them toward solutions, especially in roles without direct authority over others. At Nubank, technical leadership is embedded in collaboration, persuasion, and problem-solving across teams.

Interestingly, Lucas points out that the higher you go in the technical track, the more your work starts to resemble management — minus direct people management. At the Distinguished Engineer level, his day-to-day involves architecture decisions, strategic planning, and coordination across multiple initiatives, all requiring leadership skills as much as technical depth.

Choosing the technical path

In Nubank’s early years, engineering operated in “survival mode.” Problems appeared daily, and everyone jumped in to fix them. The first formal management roles only emerged around 2017, and at the time, many senior engineers (Lucas included) realized they preferred the technical track over people management.

Lucas became Nubank’s first Principal Engineer (IC9) in 2018, helping define the company’s technical career path. This year, he moved to Distinguished Engineer (IC10), continuing to shape the role and the architectural decisions that will enable Nubank’s next phase of growth.

Evolving architecture for hypergrowth

Scaling from zero customers in 2014 to over 122 million today required constant architectural evolution. Early on, Nubank built its systems in Clojure with Datomic, deployed on AWS using CloudFormation and AMI images. 

As growth accelerated, the stack evolved to Docker and Kubernetes, microservices, and eventually a Core Banking architecture that could support multiple products across multiple countries.

International expansion brought the challenge of localizing systems for different regulatory and market contexts. Scalability improvements, like sharding introduced in 2016, worked well for a time but eventually hit physical limits, including AWS running out of machines to match Nubank’s scaling pace. Today, large-scale architectural changes are essential to sustain growth.

Balancing standardization and creativity

In the early days, engineers organized themselves in guilds to experiment with, build and evolve the technologies and tools used by Nubank, alongside with their “main job” of delivering products. At today’s scale, there are dedicated teams for building and evolving technologies and tools, so engineers in product teams can focus on solving their product problems. 

In infrastructure and platform teams, creativity is still critical. Many of the challenges Nubank faces at scale have no ready-made solutions, pushing engineers to innovate in architecture, tooling, and operations.

Sustaining performance and well-being

Lucas divides his career into two phases: the high-intensity startup years, when work-life balance was poor, and the more structured present, where teams are organized to prevent constant firefighting. He now focuses on enabling multiple initiatives without being a bottleneck, and as a new father, on keeping work within work hours.

His advice: in the early career or early startup phase, it’s worth dedicating extra energy, as the payoff can be significant. But it’s not sustainable long-term; understanding your energy and adjusting your work accordingly is key to avoiding burnout.

Looking ahead: AI and financial innovation

Lucas sees artificial intelligence, particularly large language models, as one of the most impactful emerging technologies. While their productivity potential is clear, so are the risks of generating more output than teams can meaningfully consume or maintain. The challenge will be finding the right use cases where AI consistently delivers value.

In financial services, innovations like Brazil’s instant payment system, Pix, are transformative. Much like the before-and-after of WhatsApp, Pix has changed how people interact with money and Lucas believes similar technologies will drive deeper integration between countries and markets.

From defining Nubank’s first engineering patterns to shaping the architecture for the next decade, Lucas’s story reflects the evolution of both the company and its engineering culture. The challenges have changed, but the mission remains the same: to remove complexity from people’s lives, foster creativity, and empower teams to deliver impactful solutions. 

It’s a journey that inspires us to build the purple future together.