Kostis Saitas Zarkias is a Machine Learning (ML) Εngineer focused on Responsible AI applications, currently working on open source AI solutions & tools at Mozilla AI. He has experience in the industry building scalable ML platforms (Peltarion & Preamble) and developing guardrails for Large Language Models (Preamble). In addition, Kostis has experience in academic research (Reinforcement Learning and Meta-Learning) along with some publications and a collaboration with the Research Institute of Sweden. His studies consisted of a M.Sc in Machine Learning from KTH Royal Institute of Technology, Sweden and a B.Sc in Computer Science (Information Systems specialization) from Aristotle University of Thessaloniki, Greece, along with some additional courses on Ethics of AI and Practical Data Ethics. Kostis has also been active in many non-profit assiosiations (e.g serving as a board member of Stockholm AI in 2021-2023) and is actively involved in organizing and leading seminars, mentorship programs and discussion groups around AI ethics, privacy and open-source software.