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Curious to know what it’s like to be a Software Engineering Intern at Booking.com? We sat down with Matthew, one of our incredible interns from this summer’s programme, to look back on his journey.

I’m originally from Greece, but I’m currently based in the Netherlands. I first studied Economics, and later chose Computer Science as my second degree because I wanted something more hands-on and technical. I was curious about how the software behind the tools we use every day is actually built, and studying CS gave me the chance to dig into that! I joined Booking.com in the summer of 2025 as part of the Software Engineering Internship programme.

Booking.com is a company I’ve always admired because of the scale and the global reach it has. Millions of people use the platform every day, so the idea of contributing to something that big was really exciting. I had been keeping an eye on Booking.com’s socials and following blogs, videos and other stories from junior engineers, and that gave me a clear sense that this was the right place to grow quickly, learn from experienced engineers, and get exposure to production-level challenges.

Onboarding was smooth and structured, which made it easy to dive right in. I joined the Partner Transactional Policies Experience team. So when travellers make a booking, they want to know if it can be cancelled for free and when their card will be charged. Our team helped hotels, homes, and apartment owners configure these rules in a way that’s clear and transparent for guests. My main project was Policy Lookup: a new, unified service that brings together all data related to policies for a reservation.

Before this, policy data was scattered across different places, which made troubleshooting slow and complicated. For example, when engineers or product managers needed to check how a policy applied, they often had to search through multiple systems, which could take time and increase the likelihood of mistakes. By making everything centralised and accessible in one place, we improve performance and accessibility, making day-to-day work much easier. By the end of my internship, my work had already gone live for beta users; a very rewarding milestone!

I worked on the backend and data side using mainly Java, MySQL, Kubernetes, Docker, and GitLab for version control, while working closely with a frontend engineer who brought the interface to life. At the start of the internship, I leaned heavily on my mentor and team to navigate such a large codebase, but as I grew more confident, I tackled tasks independently, always keeping my team in the loop. I also wrote unit and integration tests to make sure everything was performing as expected.

The biggest challenge for me was adapting to the scale of Booking.com’s systems. Everything operates at such a massive level, from the size of the codebase to the number of services and deployment environments. At first it felt overwhelming, but with guidance from my mentor and team, I learned how to navigate it and eventually felt confident owning tasks independently.

Alongside the technical work, I got to experience Booking.com’s strong engineering culture; from stand-ups, retros, and demos, to cross-team collaboration and even seeing how large-scale experimentation (like A/B testing) is embedded in the company’s culture. Actively taking part in these routines taught me the value of making work visible, receiving feedback early, and using data-driven results to guide decisions – lessons I want to bring into any future team I work with!

Beyond the work itself, one of the highlights was the intern community. The Early Careers team really invested their time to make us feel at home. They were always available to answer questions, and they created plenty of opportunities for us to connect with each other. We had weekly retros just for interns, where we could share our experiences and learn from one another. On top of that, they organised social events like boat trips through Amsterdam, gelato and pizza-making activities, and more. There were also weekly workshops designed to sharpen both our technical and communication skills. Thanks to all of this, I not only levelled up technically, but also built real friendships with interns from around the world – connections that have outlasted the internship itself.

1.  Clean Code is Crucial. When your code might be read by 50 different engineers over its lifetime, every variable name and comment matters. Clean, well-tested and maintainable code when working in large systems is crucial for scale.
2. Communication is Key. Asking questions early and keeping the team in the loop saves time and avoids mistakes. Once, I spent hours trying to track down very specific data in a table, only to find out after asking a senior engineer that the same data was already available in a live service and could be fetched directly with minimal code changes, and within a few seconds. That experience showed me the value of asking early instead of trying to solve everything on your own.
3. Critical Thinking. Bring this to the table and you can make a real impact by proposing concrete improvements.

In terms of advice? Go for it. Be curious, ask questions, and don’t be afraid to dive into the deep end. Booking.com gives interns real responsibility, and the more proactive you are, the more you’ll learn and contribute. It’s a fast-paced environment, but it’s also supportive, fun, and a great place to grow as an engineer. You will definitely come away with more than you expected!

Applications for the Compass Software Engineering Internship programme open in October 2025.

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