What is a Research Engineer at Character.AI?
At Character.AI, a Research Engineer operates at the highly critical intersection of cutting-edge machine learning research and high-performance production engineering. Unlike traditional environments where research and engineering are siloed, Character.AI expects you to bridge this gap directly. You will be responsible for designing, training, and optimizing models that power open-ended conversational experiences for over 20 million monthly active users, serving an incredible scale of more than 20,000 queries per second (QPS).
The impact of this role is immediate and massive. Whether you are on the ML Systems team optimizing GPU cluster efficiency, the AI Safety & Alignment team ensuring model robustness and helpfulness, or the Multimodal team building state-of-the-art video and image generation models, your code will directly affect the daily interactions of millions of users. You are not just building abstract models; you are crafting a highly responsive, scalable, and safe digital companion.
This role is highly challenging because of the sheer scale and constraints of consumer AI. You will work with massive GPU clusters, write custom Triton kernels, design prefix-aware routing algorithms to optimize cache hit rates, and implement complex reinforcement learning from human feedback (RLHF) pipelines. It requires a rare blend of deep theoretical ML knowledge and the engineering discipline to write clean, production-ready code.




