From Coder to CTO: Izabel Jelenić on Building Croatia’s First Unicorn and Leading 800 Engineers

From a modest startup on the Adriatic coast to a global cloud communications powerhouse and Croatia’s first unicorn, Infobip‘s journey has been extraordinary. Izabel Jelenić, the company’s co-founder and Chief Technology Officer, stands at its technical heart. 

Under his leadership, Infobip has built sprawling infrastructure that includes 61 data centers, 40,000 virtual machines, and over 1.3 million physical servers. This powerful engine handles more than 10 billion messages daily, ranging from SMS and voice calls to emails and instant chat, all while supporting hundreds of in-house development teams that manage over 2,000 distinct microservices. 

Once writing code, deploying systems, and handling customer support himself, Jelenić now leads hundreds of engineers across continents while working to preserve the innovative spirit of a startup within a fast-scaling enterprise. As Infobip enters its AI-first era, he is rethinking how teams build products, how engineers stay close to customers, and how to scale without losing either quality or privacy-first culture.

You co-founded Infobip and have seen it grow from a small startup to a global tech powerhouse. How has your role as CTO evolved along this journey?

When we founded Infobip, there were just two of us, and I was doing almost everything on the technical side. I was developing, programming, deploying, providing customer support day and night, onboarding new people, hiring… Basically, everything was on my plate.

I must admit, I loved that phase because it was so active and impactful. The feedback loops were high-speed. If something went wrong, everyone knew immediately. In a small team, there’s nowhere to hide, and that intensity pushed us to constantly improve.

As the company grew and the number of people increased (there are more than 800 engineers), I had to adapt and introduce new working methods. I’m not as hands-on as I used to be, but I still try to keep that spark alive. Today, my role is more about enabling and scaling engineering across continents, ensuring our teams have what they need to innovate and succeed.

As Infobip scales its engineering across continents, how do you keep hundreds of engineers aligned while moving fast and innovating?

That’s an excellent question. As we expanded globally, we introduced engineering managers and, over time, many additional roles, like solution architects and field engineers. However, having so many layers between the customer and the engineers created distance, making it harder to understand customer problems and build the right solutions.

To address that, we’ve introduced “unfix teams.” These small, cross-functional units contain all the roles needed to build and deliver a product end-to-end. Everyone on the team shares the full context, can join customer meetings, and truly understands the customers’ needs.

This structure helps us recreate that fast feedback loop we had in the early days. It takes time — organizational change at this scale is slow — but we already see the benefits. Our engineers are more connected to the real problems and can solve them more effectively.

Infobip is now transitioning into an AI-first company. What does this shift mean for your engineering organization, and how do you build products?

It’s a fascinating shift. Traditionally, our approach has been to deeply understand the customer’s problem and design the right solution. With AI, the mindset was initially different. We suddenly had this powerful technology and were exploring what kinds of problems it could solve.

We’re now past that early experimental stage. Today, we systematically apply AI wherever it can bring value, not just in customer-facing features and products but also internally. And this is crucial: it’s not something only for engineers.

Everyone in the company, no matter their role, should understand what AI can do and identify ways to use it to boost their productivity. This change in mindset — getting people to think differently about their work — is just as important as the technology itself. When that happens, the efficiency of the entire company grows.

You’ve mentioned MCPs (Model Context Protocol) as part of your AI strategy. How are they changing your architecture and development practices?

MCPs are key because they enable AI agents to use our outputs easily. It’s crucial for us to be present on marketplaces where these AI agents operate, because they will soon be everywhere — on business systems, personal devices, really anything you can imagine.

By having an MCP, these AI agents can easily consume our services. That presence is essential, even though it may not look urgent today because AI agents are not mainstream. But their growth will be exponential.

The challenge is that enterprise customers are often reluctant to change. Their adoption cycles are slow, sometimes due to budget constraints, sometimes just the inertia of established systems. It takes longer than we would like.

Our approach is to be one step ahead: build the MCP capabilities now, be ready with solutions, and partner with customers willing to innovate early. That way, we can get feedback and refine our offering before the market fully catches up.

What makes Eastern European engineers so strong as product-oriented engineers, not just good coders?

Engineers from the CEE region are exceptionally good at understanding the whole problem, not just their piece. Part of that comes from history. Engineers from this region traveled worldwide for generations, building everything from significant architectural structures to complex machinery.

Even centuries ago, they were valued as resourceful builders and problem solvers. That mindset stayed with us. This drive to understand the problem and use creativity to solve it. And that is very close to what product engineering is about: not just writing code but also thinking holistically about the solution.

What do you specifically look for when hiring new engineers at Infobip, and how do you develop them into world-class product builders and leaders?

We focus heavily on mindset and culture fit. How someone approaches a problem, how they think, and how they collaborate within a team are all very hard to change later.

Technology and tools can always be learned, but attitude is much harder to teach. If someone’s mindset doesn’t fit our culture, it can create problems for the whole team later. So we try to detect that early.

One thing we do is have a second round of interviews after the technical part, where the candidate speaks with an engineer who is not involved in the hiring decision. This person has no deadlines or pressure to fill a position, so they can be more objective.

Their role is to evaluate attitude, cultural fit, and potential, and to spot any red flags. This approach has proven very useful for us. It helps ensure we hire people with the skills and mindset to grow into world-class product builders and future leaders.

How have you personally changed as a CTO — from writing code and designing systems to becoming a business-focused technology leader?

I hope I haven’t changed too much, though perhaps that’s for others to judge rather than me. What I do know is that I still miss the deeply technical, hands-on work that first drew me to technology. That was the foundation of why I co-founded Infobip in the first place.

These days, my role no longer allows me to be immersed in code or system design daily, so I’ve had to become very intentional about how I spend my time. I make a conscious effort to stay close to our technologies, understand challenges there, and remain intellectually connected to the craft, even if I’m no longer the one building it myself.

Looking back, what pivotal decisions or cultural principles allowed Infobip’s engineering to scale without losing quality?

There are a few core principles that have served us well. One of the most important is the mindset that nothing is beneath you — there’s no such thing as “that’s not my job.” Regardless of their role, everyone is expected to take ownership and be willing to get their hands dirty when needed.

This creates a culture where people hold themselves accountable, perform quick checks, and make thoughtful decisions daily without constant oversight. It also helps candidates self-select: When they see how we work, they can decide early on if this is an environment where they will thrive. That clarity — both internally and externally — has helped us scale without diluting our standards.

How do you maintain a privacy-first business model despite the introduction of AI?

It’s a challenge, mainly as AI often depends on large amounts of data. But there are ways to reconcile the two.

Infobip operates in a very geographically distributed way. With 61 data centers, 40,000 virtual machines, and over 1.3 million physical servers, many of the regions we serve have strict regulations that prevent data from leaving the country.

So we design our AI systems to be deployed locally, trained on data within those boundaries, and used within a strictly limited scope.

Even with that limited scope, these models can still provide highly effective results, ensuring no data is transmitted externally or stored in centralized cloud environments.

Ultimately, it’s a combination of technical design and transparent communication. We need to explain to our customers exactly how their data is handled, demonstrate our safeguards, and build trust that privacy will never be compromised in pursuit of AI-driven innovation.

How do you ensure the engineering team maintains constant contact with users and their actual needs?

Engineers often drift further away from customers as companies grow. Communication gets routed through layers of managers, product owners, or support teams. While that may seem efficient, it creates a real risk: engineers start building in isolation without fully understanding the people they’re building for.

In Infobip’s early days, it was the opposite. Customers could directly message any engineer on Skype, and that immediacy kept everyone aligned. Over time, we introduced more structured tools and processes like Jira, which helped with organization and created distance.

To close that gap again, we’re now restructuring around small cross-functional “unfixed teams” I mentioned. These teams include all the roles needed to own a product end-to-end, and everyone — engineers included — is encouraged to join customer calls, ask questions, and hear feedback firsthand.

It’s incredibly valuable. When engineers directly experience the customer’s perspective, they gain intuition about what truly matters, leading to better, more thoughtful solutions.

What advice would you give young engineering talents who aspire to become impactful tech leaders or CTOs?

Everyone defines success in their own way, and there’s nothing wrong with that. But if you aspire to become a technology leader — whether a CTO or something else — you must recognize that growth requires investment.

Younger engineers today focus heavily on strict work-life balance and eight-hour days. That balance is essential, of course. But when you’re early in your career and have fewer personal obligations, it’s also the best time to go deep, explore, and push yourself further.

Be curious. Seek out challenges. Volunteer for work that stretches you beyond your comfort zone. Technical skills are essential, but just as critical is developing a broad understanding of how technology connects to businesses and people.

If you combine that mindset with hard work and persistence, you’ll naturally grow into someone who can lead — not just write code, but shape the future of technology.

Building and scaling a unicorn from the Adriatic coast to global markets requires more than just technical excellence—it demands a culture that balances startup agility with enterprise discipline. As Izabel demonstrates through Infobip’s journey, successful CTOs must evolve from hands-on builders to strategic enablers while preserving the direct customer connection and ownership mindset that drives innovation. The transition to AI-first operations, combined with privacy-first principles and distributed infrastructure, represents the next frontier for technology leaders navigating the complexities of global scale.

Don’t miss the chance to connect with Izabel Jelenić at How to Web Conference 2025.

Whether you’re an aspiring CTO, an engineering leader scaling teams, or an entrepreneur curious about building privacy-first AI systems, Izabel’s insights offer practical wisdom from someone who’s navigated the complete journey from startup co-founder to unicorn CTO. Meet him at How to Web Conference 2025!