Principal AI/ML Engineer

Stockholm Stockholm County 111 57 Sweden 21 days ago Job Description: Principal AI/ML Engineer | AI Center of Excellence (ACE) At King, we create games that are played by millions around the world. To keep raising the bar on quality and player experience, we invest deeply in applied AI/ML — from improving how we build game content to optimising live game decisions at scale. About the role We’re looking for a passionate and creative Principal AI/ML Engineer to join the ML Special Projects team, part of King’s AI Center of Excellence (ACE) — a central team that partners with game and shared tech teams to build, ship, and scale machine learning systems that deliver real product impact. As a member of the team, you will be working closely with other AI/ML Engineers, Data Scientists, and Product Managers supporting them to develop and operationalize ML models as part of King’s central AI/ML initiatives. This is a hands-on, high-ownership role. You will take problems from discovery and experimentation through to reliable production systems, and help set engineering standards for how ML is built and adopted across King. You are someone who is interested in pushing the boundaries of applied ML in our products and production, improving the experience for over 250 million monthly active users in our games! What you’ll work on You’ll work on a range of applied ML problems across King, with a strong focus on initiatives that have clear product and production impact. While priorities will evolve, much of the work will center around the following areas: Level, Content & Production Automation ML-driven playtesting, quality signals, and simulation to accelerate iteration of content creation and evaluation Content evaluation and optimisation to improve the speed, reliability, and scalability of level production workflows Where appropriate, reinforcement learning and other sequential or simulation-based approaches to model gameplay and player behavior Decision Automation Models and decision policies which improve the experience of our players Online learning and experimentation systems (e.g., contextual bandits or similar approaches) with strong safety and evaluation guardrails Measurement frameworks that connect proxy metrics to long-term business and player outcomes Additional applied ML initiatives Representation learning and player modelling on large-scale event or time-series data to enable downstream use cases Foundational ML capabilities, tooling, or services that help product teams adopt and operate ML more effectively Exploration of new ML-driven opportunities as games, tools, and business needs evolve What you’ll do Drive end-to-end ML delivery : problem framing → data & features → modelling → evaluation → deployment → monitoring and iteration Build and maintain robust pipelines (batch and/or streaming) for training and inference, with strong reproducibility and observability Design offline + online evaluation strategies, balancing proxy metrics for game optimization Partner with engineers, data scientists, product managers, and designers across the business to translate opportunities into shippable systems Raise the bar on applied ML engineering best practices : reliable releases, clear scoping, defensible trade-offs, documentation, and maintainable handover Provide technical leadership : coach others, influence architecture, and contribute to long-term ML platform and product strategy What we’re looking for (requirements) Proven track record delivering production ML systems end-to-end in consumer products or similarly complex environments Strong software engineering skills (Python), with experience in modern ML frameworks (e.g., PyTorch/TensorFlow) Experience building or operating data/ML pipelines at scale (batch and/or streaming), and working effectively with large datasets Solid understanding of experiment design, evaluation and metrics, including how to reason about bias, drift, and measurement pitfalls Deep expertise in at least one of the following areas (and willingness to learn others):1. causal inference2. contextual bandits / online learning & decisioning3. reinforcement learning / simulation-based evaluation Strong operational mindset : CI/CD, infrastructure-as-code or equivalent, monitoring/alerting, and debugging in real-world systems Excellent communication, collaboration, and stakeholder management skills: ability to align stakeholders and drive progress across teams Strong leadership skills to coach and mentor more junior team members Nice to have Experience building ML tooling/platform capabilities Experience in games (mobile, console, casual, or otherwise) and curiosity about how gameplay connects to player experience and spending behavior Contributions to open source or community ML tooling Our tech environment (examples) Python, modern ML stacks (PyTorch/TensorFlow), experiment tracking and evaluation at scale Batch and streaming data processing; cloud data platforms and ML infrastructure Git-based workflows, CI/CD, infrastructure-as-code, monitoring and observability practices Google Cloud, BigQuery, SQL Work on ML problems that ship into real products, not just prototypes Operate at massive scale, with real constraints and real impact Influence how ML is built and adopted across multiple teams and domains Join a group that values pragmatic engineering, principled measurement, and clear communication Stockholm, London With a mission of Making the World Playful, King is a leading interactive entertainment company with more than 20 years of history of delivering some of the world’s most iconic games in the mobile gaming industry, including the world-famous Candy Crush franchise, as well as other mobile game hits such as Farm Heroes Sag a. King games are played by more than 200 million monthly active users. King, part of Microsoft (NASDAQ: MSFT), has Kingsters in Stockholm, Malmö, London, Barcelona, Berlin, Dublin, San Francisco, New York, Los Angeles and Malta. More information can be found atKing.comor by following us onLinkedIn,@lifeatkingon Instagram, or@king_gameson X.