What is a Data Scientist at Cohere?

At Cohere, the Data Scientist role is pivotal to our mission of building machines that understand the world and making massive language models accessible to all. Unlike traditional data science roles that may focus heavily on business analytics or simple regression models, a Data Scientist here operates at the cutting edge of Natural Language Processing (NLP) and Generative AI. You are not just analyzing data; you are shaping the inputs and evaluation methods that drive the performance of industry-leading Large Language Models (LLMs).

This position sits at the intersection of applied research and product engineering. You will work on complex challenges such as improving model factual accuracy, designing robust evaluation frameworks for generative tasks, and curating high-quality datasets that fuel model training. Your work directly impacts how our enterprise customers leverage AI to solve real-world problems, from semantic search to content generation.

We look for individuals who are comfortable navigating ambiguity. You will likely work within a cross-functional team of researchers and engineers, translating high-level research concepts into scalable, production-ready solutions. If you are passionate about the mechanics of Transformers, the nuances of data quality in deep learning, and the ethical deployment of AI, this role offers a unique platform to define the future of human-machine interaction.

Getting Ready for Your Interviews

Preparing for an interview at Cohere requires a shift in mindset from standard coding interviews to a focus on practical ML application and research intuition. You should approach your preparation holistically, ensuring you can code fluent Python while also debating the architectural trade-offs of modern neural networks.

We evaluate candidates based on several core competencies:

Deep Learning & NLP Fundamentals This is the bedrock of your assessment. Interviewers will test your theoretical understanding of neural network architectures, specifically Transformers. You must be able to explain concepts like attention mechanisms, positional encodings, and backpropagation clearly. We look for candidates who understand why these architectures work, not just how to import them.

Practical Implementation & Coding Beyond theory, you need to demonstrate hands-on capability. You will be evaluated on your ability to write clean, efficient code to solve data manipulation and modeling problems. Expect to work in environments like Google Colab or a local IDE during the interview. We assess how you structure your code, handle edge cases, and translate mathematical formulas into working functions.

Research Intuition & Problem Solving We value candidates who can think like researchers. You will face open-ended problems where you must propose solutions, design experiments, and interpret results. We look for a scientific approach to debugging models—how you isolate variables, analyze failure modes, and iterate on your approach based on empirical data.

Interview Process Overview

The interview process at Cohere is rigorous and designed to provide a comprehensive view of your technical depth and cultural alignment. It typically begins with a recruiter screen to verify your background and interest. Following this, you will enter a series of technical engagements. The process is known for being interactive and discussion-based rather than purely interrogative. We want to see how you collaborate on hard problems.

Candidates should expect a mix of live coding sessions and research deep dives. Unlike generic software engineering loops, our process heavily emphasizes your specific domain knowledge in machine learning. You may be asked to complete a take-home project or a live task involving a notebook environment, where you must implement a solution and explain your reasoning in real-time. The final stage usually involves a "super day" or a loop of back-to-back interviews covering research, coding, and behavioral alignment.

This timeline illustrates the typical progression from application to offer. Note the emphasis on multiple technical touchpoints. Use the time between the initial screen and the technical rounds to refresh your knowledge of PyTorch/TensorFlow and read up on recent NLP literature. The "Research Deep Dive" is often the most challenging step, so allocate significant energy to preparing for high-level architectural discussions.

Deep Dive into Evaluation Areas

Your interviews will dissect your skills across three to four major pillars. Based on recent candidate experiences, the bar is high for both theoretical depth and practical execution.

Machine Learning Fundamentals & Architecture

This is the most critical technical area. You generally cannot pass the interview without a strong grasp of deep learning mechanics. Interviewers will probe your understanding of the mathematical foundations of modern AI.

Be ready to go over:

• Transformer Architecture: Self-attention, multi-head attention, encoder-decoder structures, and why they replaced RNNs/LSTMs.
• Optimization: Gradient descent variants (Adam, SGD), loss functions, and handling vanishing/exploding gradients.
• Regularization & Tuning: Dropout, batch normalization, and hyperparameter tuning strategies.
• Advanced concepts: Tokenization strategies (BPE, WordPiece), positional embeddings, and scaling laws.

Example questions or scenarios:

• "Explain the mathematical mechanism of the Attention layer in a Transformer."
• "How would you address a model that is overfitting on a small dataset?"
• "Walk me through the differences between BERT and GPT architectures."

Practical Coding & Data Manipulation

Cohere is a company of builders. You will be asked to write code that is not only functional but also clean and Pythonic. These rounds often simulate real day-to-day tasks using notebooks.

Be ready to go over:

• Data Processing: Using Pandas/NumPy to clean, reshape, and tokenize text data.
• Model Implementation: Implementing specific layers or loss functions from scratch in PyTorch or NumPy.
• Algorithm Design: Standard algorithmic problems, but often with a data-centric twist.

Example questions or scenarios:

• "Given a raw dataset of text, write a pipeline to clean it and prepare it for training."
• "Implement the softmax function from scratch and handle numerical stability issues."
• "Here is a problem description; use this Google Colab notebook to implement a solution."

Research & Project Deep Dive

In this section, you will discuss your past work or a hypothetical research problem. This is your chance to show your passion and your ability to communicate complex ideas.

Be ready to go over:

• Project Ownership: End-to-end walkthroughs of ML projects you have led, focusing on the "why" behind your decisions.
• Critical Analysis: Discussing the limitations of current LLMs and proposing novel solutions.
• Evaluation Metrics: How to measure success in generative tasks (BLEU, ROUGE, human evaluation, perplexity).

Example questions or scenarios:

• "Tell me about a time your model failed. How did you diagnose the issue?"
• "If we wanted to improve the factual accuracy of our model, how would you approach the research?"
• "Describe a recent research paper you read and its implications for our work."

The word cloud above highlights the most frequently occurring terms in our interview feedback. Notice the dominance of Transformers, Deep Learning, and Coding. This signals that while general data science skills (like SQL or A/B testing) are useful, your preparation should be heavily weighted toward Neural Network architecture and engineering.

Key Responsibilities

As a Data Scientist at Cohere, your daily work will be dynamic and highly technical. You will not simply be "pulling data"; you will be an integral part of the model development lifecycle.

• Model Development & Evaluation: You will design and implement experiments to evaluate model performance. This involves creating new benchmarks, analyzing model outputs for bias or hallucinations, and fine-tuning models on specific domains.
• Data Strategy & Curation: High-quality data is the fuel for our models. You will be responsible for identifying high-value datasets, building pipelines to clean and process this data at scale, and ensuring data diversity.
• Applied Research: You will bridge the gap between pure research and product. This means reading the latest papers (often from our own team) and prototyping ways to integrate those findings into our API and platform.
• Cross-Functional Collaboration: You will work closely with the engineering team to optimize model inference and with the product team to understand customer needs, translating vague business requirements into concrete technical specifications.

Role Requirements & Qualifications

To succeed in this role, you need a blend of software engineering rigor and scientific curiosity.

• Must-have skills:

  • Strong Python Proficiency: You must be fluent in Python for data manipulation and modeling.
  • Deep Learning Frameworks: Extensive experience with PyTorch (preferred) or TensorFlow/JAX is essential.
  • NLP Expertise: A solid grounding in modern NLP, specifically Transformer-based models and LLMs.
  • Mathematical Foundation: Strong grasp of linear algebra, probability, and calculus as they apply to ML.

• Nice-to-have skills:

  • Research Track Record: Publications in top-tier conferences (NeurIPS, ICLR, ACL) are a significant plus.
  • Distributed Training: Experience training models on large-scale GPU clusters.
  • Specialized Domain Knowledge: Experience in healthcare data, code generation, or reinforcement learning (RLHF).

Common Interview Questions

The following questions are representative of what you might face. They are designed to test your depth of understanding and your ability to apply concepts to new problems.

Technical & Theory

• "How does Multi-Head Attention differ from Single-Head Attention, and what benefit does it provide?"
• "Explain the concept of 'vanishing gradients' and how residual connections help solve it."
• "What is the difference between discriminative and generative models?"
• "How do you handle out-of-vocabulary words in NLP models?"

Coding & Implementation

• "Write a function to compute the Intersection over Union (IoU) for object detection (or similar metric for NLP spans)."
• "Implement a custom data loader in PyTorch that handles variable-length sequences."
• "Given a list of sentences, find the top K most similar pairs using cosine similarity."

Behavioral & Situational

• "Describe a time you had a technical disagreement with a team member. How did you resolve it?"
• "Tell me about a project where you had to learn a new technology quickly."
• "How do you prioritize tasks when you have multiple deadlines and ambiguous requirements?"

These questions are based on real interview experiences from candidates who interviewed at this company. You can practice answering them interactively on Dataford to better prepare for your interview.

Frequently Asked Questions

Q: How much preparation time is recommended? For a role of this caliber, successful candidates typically spend 3–4 weeks preparing, specifically focusing on refreshing deep learning theory and practicing coding problems in a notebook environment.

Q: Is the coding round LeetCode-style or practical? It is a mix, but leans heavily towards practical. While you should know your algorithms, you are more likely to face a task that involves implementing a specific ML component or data pipeline in a notebook than a generic dynamic programming puzzle.

Q: What differentiates a 'Hire' from a 'No Hire'? Strong candidates show intuition. They don't just know the definitions; they can explain why a certain architecture is better for a specific problem. They also communicate their thought process clearly during coding tasks.

Q: Does Cohere offer remote work? Yes, Cohere supports a hybrid and remote-friendly culture, though specific requirements may vary by team and location (e.g., London vs. Toronto vs. San Francisco).

Q: What is the culture like for Data Scientists? The culture is research-driven but product-focused. It is collaborative and intellectually honest. You are encouraged to challenge assumptions and propose new ideas, regardless of your seniority.

Other General Tips

• Read "Attention Is All You Need": It sounds obvious, but you should know the Transformer paper inside and out. It is the foundation of everything we do.
• Practice in Colab: Get comfortable coding in a notebook environment without IntelliSense. You need to be able to write runnable code from scratch.
• Know Your Resume: Anything on your resume is fair game. If you list a specific algorithm or paper, expect to be grilled on the minute details of it.
• Ask Questions: In the research discussions, treat the interviewer as a peer. Asking insightful questions about the team's current challenges shows that you are engaged and thinking critically.
• Focus on Clarity: When explaining complex math, start high-level and drill down. Don't get lost in the weeds unless asked. Clear communication of complex topics is a key skill we evaluate.

Summary & Next Steps

Becoming a Data Scientist at Cohere is an opportunity to work at the forefront of the AI revolution. You will be challenged to solve unsolved problems and build systems that are changing how the world interacts with technology. The role demands excellence in both engineering and research, but the reward is the chance to work with some of the brightest minds in the industry on truly impactful products.

To succeed, focus your preparation on the intersection of theory and code. deeply understand the architecture of Large Language Models, practice implementing them, and be ready to discuss your past work with passion and precision. We are looking for builders who are curious, humble, and ready to push the boundaries of what is possible.

This salary data represents the base compensation range for this position. Total compensation at Cohere typically includes significant equity packages and benefits, reflecting the high impact and competitive nature of the role.

Good luck with your preparation. We look forward to seeing what you can build.