Who We Are

We are a Sofia based company and care about the city we live in. At Theoremus, we have a common vision that we want to share and live in cleaner, healthier, happier and better cities overall, and we know that to live this dream today means we have to combine skills, reason and passion in a bold, new way. We’ve gained expertise and are currently focused on two main areas:

• Mobility аnalytics & ticketing – We pride ourselves in developing Sofia’s public transportation ticketing system, and especially its online components, such as the QR tickets and the debit card payments. Furthermore, on top of that, we have developed its advanced analytics sub-system, which measures the behavioural patterns of public transit passengers, and aims to optimise for a frictionless experience. Our goal is to continuously enhance user experience and encourage people to limit the use of private vehicles, and thus improve urban mobility, traffic and air quality in the cities where your friends and family live.
• Smart waste management – Our know-how in the waste management sector has been disseminated into multiple projects throughout Bulgaria and Spain. We have developed big IoT systems consisting of thousands of sensors attached to trucks and containers. The aim of these systems is to deploy data science methods in order to optimise the circular economy lifecycle and make waste taxation fairer.

What We’re Looking For

We’re looking for a skilled developer who can orchestrate exceptional mobile experiences. Here’s what we’d love to see:

• Strong proficiency in JavaScript ES6+ (experience with TypeScript is a plus).
• Experience building mobile applications using React Native and managing workflows with Expo.
• Familiarity with Redux and a general understanding of approaches to state management.
• Understanding of Native Modules is a plus.
• Familiarity with Android Studio.
• Experience working with RESTful APIs.
• Knowledge of Kotlin or Java is advantageous.
• A problem-solving mindset – we love people who ask why before jumping into solutions.
• Eagerness to learn, experiment, and grow – technical expertise can be developed, but curiosity and motivation are priceless.

Professional Growth & Domain Expertise
You’ll expand your expertise by working on unique challenges that impact thousands of users daily:

• Tackle complex technical problems that require innovative mobile solutions.
• Gain experience with high-performance applications serving diverse user needs.
• Build expertise in developing systems that handle real-time data processing and visualization.
• Work across multiple domains and business verticals to create versatile solutions.
• Shape product architecture and technology decisions in a collaborative environment.
• Master the balance between user experience excellence and system performance.

What You’ll Do

• Develop and improve mobile applications.
• Create intuitive interfaces.
• Work closely with UX designers, backend developers, and data scientists to bring new features to life.
• Contribute ideas and solutions – if you see something that can be better, we want to hear it.
• Learn from experienced engineers and grow in a supportive team.

What We Offer

• Competitive salary and real career growth in an innovative company.
• Additional health insurance and Multisport card to keep you healthy.
• Public transport card – because we believe in sustainable mobility.
• 25 days of annual paid leave – because we know rest is important.
• Fridays that end at 2 PM – because balance matters.
• A team that values learning, creativity, and having fun together.
• An amazing office in Sofia’s city center with a 360-degree panoramic view and a summer terrace for coffee, networking, and cake (we love cake).
• A mission that matters – your work will improve city life for thousands of people.

What We Believe In

• We don’t just write code – we build systems that make cities smarter. Part of our values:
• Services over monoliths – Keep things modular and scalable.
• Prototyping before development – Test before committing.
• Science over technology – Data-driven decisions over hype.
• Trust over processes – You get ownership, not micromanagement.
• People and sustainability first – Tech should serve people, not profits alone.
• AI as a tool to eliminate repetitive coding tasks – so our team can focus on solving complex, meaningful problems that drive innovation.
• That’s the short version. We know we’re not alone on this journey.