I know this because I was one of the very first engineers at Wise, part of the early team that built its payment infrastructure and real-time currency pricing system and played a key role in building one of the biggest fintechs in the world.

Wise's engineering beginnings

Wise, founded in 2011 by Taavet Hinrikus and Kristo Käärmann, aimed to eliminate the high costs and inefficiencies of international money transfers. What started as a simple idea quickly gained traction, but the founders needed a strong technical team to bring their vision to life.

Back in the early days, before Wise became the billion-dollar company it is today, it didn't even have its own in-house engineering team. Instead, its founders recognised the potential of Ukrainian tech talent. In fact, the very first implementation of Wise’s platform was built by a Ukrainian developers. I had the honour to be a part of the first engineering team that was initially hired as an outsourced team together with our fellow Estonian and other tech professionals. We played a key role in building the foundation of Wise’s payment infrastructure.

I joined Wise as the 4th engineer and the 11th employee. It was an exciting time, a true startup environment where everyone was deeply invested in the mission. Initially, the Ukrainian team was brought in as an outsourced engineering resource. Over time, this team transitioned from being an external resource to becoming full-time Wise employees, and I got to witness firsthand how the company grew from 11 to 2,500 employees – that was the total headcount of Wise at the time when I moved on to my next career stage as a technical co-founder of Moss. Now, Wise has more than 5,000 employees across 15+ key locations worldwide.

Building the infrastructure that powered Wise’s growth

The Ukrainian team played a crucial role in building the infrastructure that powered Wise's hypergrowth. In those early years, our Ukrainian team was responsible for some of Wise’s most critical technical breakthroughs:

P2P currency exchange system – initial model of money transfer was built around the idea of connecting 2 sides looking to exchange currency at real exchange rate. We build a system that allows matching people and currency directions. Ensuring there is enough liquidity to cover the exchange.

Request money ability – Wise started as a cheap and easy way of sending the money abroad​, but we quickly realised that the ability to request money from individuals or businesses was a real need. A team in Ukraine, including me, have built an initial version of this product.

Launching currency routes – adding new currency routes, allowing customers to send money to more countries. This was crucial for Wise’s growth and world recognition. As part of the early team – we built numerous currency routes and opened new markets.

Scaling Wise's engineering team from a small startup to a global operation with over 2,500 employees was a challenging but rewarding experience. We built systems and processes that allowed us to manage engineering teams effectively.

Engineering at Wise. Simplicity & scale

Wise has always been a mission-driven company. From day one, our goal was clear – make international money transfers as low-cost as possible, eventually aiming for free. This mission shaped every decision we made, and at the core of it all was the customer. We obsessed over creating a product that truly served their needs, listening carefully to their pain points and relentlessly improving the experience.

The three pillars of Wise

As we set out to build Wise, we identified three fundamental pillars that would define the product: speed, convenience, and price. These became the foundation upon which we structured our engineering and product teams. Every team focused on enhancing one of these aspects, ensuring that we consistently delivered faster, easier, and more cost-effective transfers for our users.

The early days: speed and agility

In the early days, our priority was clear – build fast and move quickly. Startups thrive on agility, and we embraced this mindset fully. Speed was essential, not just in our product but also in decision-making and execution. We operated with a sense of urgency, rapidly iterating and improving based on real user feedback.

Scaling up: from speed to stability

As Wise grew and our user base expanded significantly, the dynamics began to shift. The early-stage startup mentality of moving fast and breaking things had to evolve. Reliability and scalability became critical as millions of users around the world depended on our service for important financial transactions. We transitioned from a mindset of rapid experimentation to one that balanced innovation with robustness, ensuring that Wise remained both cutting-edge and dependable.

Wise was initially built as a rather monolithic web application. Over time, with the efforts of the rapidly growing engineering teams, it evolved into a distributed, service-oriented microservices architecture to achieve scalability. We started building an architecture that allowed each component of the system to scale independently. Instead of monolithic banking systems, we moved on to building lightweight services that could handle different parts of a transaction. As of 2021, we had more than a hundred microservices working together.

With millions of users and billions in transactions, Wise didn’t have the luxury of growing slowly, so we had to handle increasing transaction volumes while keeping fees low. The challenge was:

• How do we move billions across multiple financial networks in real time?
• How do we keep our system efficient as we scale from thousands to millions of users?
• How do we ensure security and compliance without slowing down innovation?

This is how we managed to grow the system without increasing costs or failures:

Modular, service-based architecture – instead of a monolithic system, over time  we built independent, scalable services. If transaction volume spiked, we could scale specific components without affecting the rest of the system.

Global data replication – we used distributed databases that replicated data across multiple regions. This ensured fast, reliable payments worldwide, regardless of user location.

Real-time currency pricing engine – unlike banks that update rates once or twice a day, we built a system that continuously synced forex data, ensuring users always got the best possible exchange rate.

Load balancing for seamless performance – traffic was dynamically routed across multiple servers, preventing bottlenecks and ensuring smooth performance even during demand spikes.

What this means for the future of fintech

There’s a common belief that the biggest fintech companies can only come from Silicon Valley, London, or Berlin. But Wise proved that this isn’t true.

Looking back, here’s what I’d tell fintech startups that are trying to scale today:

Outsourcing isn’t just about cutting costs – it can build your core product. Wise started with an outsourced team, but those engineers became an integral part of its long-term success.

Eastern Europe is a fintech powerhouse. From Wise to Revolut to Monobank, many of the biggest fintechs have roots in this region.

Keep engineering simple – the best fintech products aren’t the most complex, they’re the most efficient.

Build for scale from day one – don’t just launch an MVP, build an architecture that can grow without breaking.

You don’t need to be in a major startup hub to build something global. Wise’s infrastructure was built by a distributed team – the right talent matters more than the right location.

The journey continues

Building Wise has been a journey of continuous learning and adaptation. What started as a bold vision to disrupt the outdated financial system has become a global product that millions rely on. While the way we operate has evolved, the mission remains unchanged – making money transfers fairer, cheaper, and better for everyone.

The early days laid the foundation for what Wise is today. And as Wise continues to grow, and stay true to the principles that got us here: putting customers first, innovating relentlessly, and never losing sight of the mission that started it all.