Applied Scientist interview preparation.
A role-focused question set spanning coding, ML fundamentals, system design, GenAI, and project depth where the evidence supports it.
How is BERT different from GPT?GenAI & LLM · medium · Evidence 88/100Explain Transformer architecture and each major component.GenAI & LLM · medium · Evidence 88/100How should dropout behave at test time?ML Fundamentals · medium · Evidence 82/100Serialize and Deserialize Binary TreePython & DSA · hard · Evidence 80/100Explain the attention mechanism in a Transformer.GenAI & LLM · medium · Evidence 78/100Explain the bias-variance trade-off.ML Fundamentals · easy · Evidence 77/100Explain linear regression assumptions and failure modes.ML Fundamentals · medium · Evidence 77/100Walk through the toughest ML problem you solved and defend the approach.Project & Behavioral · hard · Evidence 77/100Implement Byte Pair Encoding.ML Coding & PyTorch · hard · Evidence 77/100When would you use RMSE instead of MAE?ML Fundamentals · medium · Evidence 77/100Explain PCA and when you would use it.ML Fundamentals · medium · Evidence 77/100Implement an in-place sorting algorithm and analyze every loop.Python & DSA · medium · Evidence 77/100Design an efficient sparse-matrix representation.ML Coding & PyTorch · medium · Evidence 77/100Solve the maximum-points-on-a-line problem.Python & DSA · hard · Evidence 77/100How do tree-based algorithms choose splits and generalize?ML Fundamentals · medium · Evidence 77/100Design an end-to-end image-and-text pipeline to predict document aspect ratio.ML System Design · hard · Evidence 77/100How does multiclass logistic regression work?ML Fundamentals · medium · Evidence 77/100Design a color suggestion system.ML System Design · hard · Evidence 77/100Design entity matching across different Alexa skills.ML System Design · hard · Evidence 77/100Compare covariate shift and label drift.ML Fundamentals · medium · Evidence 77/100Implement self-attention.ML Coding & PyTorch · hard · Evidence 77/100What does R-squared measure?ML Fundamentals · easy · Evidence 77/100How would you formulate and interpret R-squared for a regression system?ML Math · medium · Evidence 77/100Solve a variation of Longest Increasing Path in a Matrix.Python & DSA · hard · Evidence 77/100What are the trade-offs of downsampling the majority class?ML Fundamentals · medium · Evidence 77/100Compare Thompson sampling and epsilon-greedy.ML Fundamentals · hard · Evidence 77/100How would you handle cold start for new ads?ML System Design · medium · Evidence 77/100When would you use a one-tailed vs two-tailed t-test?ML Fundamentals · medium · Evidence 77/100Implement masked self-attention.ML Coding & PyTorch · hard · Evidence 77/100How does a multilayer perceptron learn nonlinear functions?ML Fundamentals · medium · Evidence 77/100Implement the transpose of a sparse matrix efficiently.ML Coding & PyTorch · medium · Evidence 77/100When would you choose gradient boosting over an SVM from a business perspective?ML Fundamentals · hard · Evidence 77/100Why can offline metrics look better than online metrics?ML Fundamentals · hard · Evidence 77/100Explain the exploration-exploitation trade-off.ML Fundamentals · medium · Evidence 77/100Design local search rankingML System Design · medium · Evidence 77/100Explain core NLP and deep-learning concepts used in an Alexa system.GenAI & LLM · medium · Evidence 77/100Solve merge intervals.Python & DSA · medium · Evidence 77/100Which statistical tests can detect distribution drift?ML Fundamentals · hard · Evidence 77/100Predict whether an old post is good for MemoriesML System Design · medium · Evidence 77/100Predict the language of Instagram postsML System Design · medium · Evidence 77/100How would you vectorize a K-means implementation?ML Coding & PyTorch · hard · Evidence 77/100Explain binary logistic regression.ML Fundamentals · easy · Evidence 77/100How would you learn a new policy from logged data collected by an old policy?ML Fundamentals · hard · Evidence 77/100Implement K-means from scratch.ML Coding & PyTorch · medium · Evidence 77/100Design News Feed rankingML System Design · medium · Evidence 77/100Why and when would you ensemble models?ML Fundamentals · medium · Evidence 77/100How would you handle an imbalanced dataset?ML Fundamentals · medium · Evidence 76/100How do you calibrate a classifier?ML Fundamentals · medium · Evidence 75/100What is maximum-likelihood estimation?ML Fundamentals · medium · Evidence 75/100How would you improve detection of very small objects?ML Fundamentals · hard · Evidence 75/100How do learning-rate schedules affect training?ML Fundamentals · medium · Evidence 75/100Find and print a path from a source to a destination through obstacles.Python & DSA · medium · Evidence 75/100Walk through an ML project and defend your technical decisions.Project & Behavioral · medium · Evidence 75/100Write the mathematical form of Wasserstein distance and explain it.ML Math · hard · Evidence 75/100Explain regularization and why it works.ML Fundamentals · easy · Evidence 75/100How does an LSTM differ from a Transformer?GenAI & LLM · medium · Evidence 75/100How would you design a loss function that encourages recommendation diversity?ML Fundamentals · hard · Evidence 75/100How do linear and logistic regression differ?ML Fundamentals · easy · Evidence 75/100What is the Hoeffding inequality and when would you use it?ML Math · hard · Evidence 75/100Explain Transformer fundamentals for a multimodal role.GenAI & LLM · medium · Evidence 75/100Explain LoRA and why it reduces fine-tuning cost.GenAI & LLM · medium · Evidence 75/100Implement MinStack with O(1) minimum lookup.Python & DSA · medium · Evidence 75/100Design a recommendation system for a product scenario.ML System Design · hard · Evidence 75/100Implement single-head attention in PyTorch.ML Coding & PyTorch · hard · Evidence 75/100Design a system to detect copyright violations on YouTubeML System Design · hard · Evidence 75/100Explain how deep neural networks differ from shallow models.ML Fundamentals · easy · Evidence 75/100What was your most challenging GenAI or ML project?Project & Behavioral · medium · Evidence 75/100Compare common loss functions and when to use them.ML Fundamentals · medium · Evidence 75/100Implement KL divergence in Python.ML Coding & PyTorch · medium · Evidence 75/100What is the time complexity of matrix inversion?ML Math · medium · Evidence 75/100Explain attention in modern neural networks.GenAI & LLM · medium · Evidence 75/100Add a causal mask that hides future tokens.ML Coding & PyTorch · hard · Evidence 75/100How do you account for observed and unobserved confounding?ML Fundamentals · hard · Evidence 75/100Tell me about the most difficult technical project you handled.Project & Behavioral · medium · Evidence 75/100How do you reason about time and space complexity in ML-adjacent coding?Python & DSA · medium · Evidence 75/100Explain ResNet and why residual connections help.ML Fundamentals · medium · Evidence 75/100What are sparse-attention methods in Transformers?GenAI & LLM · hard · Evidence 75/100What does dropout do during neural-network training?ML Fundamentals · easy · Evidence 75/100What are the key design choices in a computer-vision model?ML Fundamentals · medium · Evidence 75/100Explain core NLP modeling choices.GenAI & LLM · medium · Evidence 75/100Describe the Segment Anything Model (SAM) and how it worksML Fundamentals · medium · Evidence 75/100Implement self-attention from scratch in code.ML Coding & PyTorch · hard · Evidence 75/100Generate valid word combinations from a word list.Python & DSA · medium · Evidence 75/100Design a small polite LLM that runs on a phoneGenAI & LLM · hard · Evidence 75/100Implement multi-head attention in PyTorch.ML Coding & PyTorch · hard · Evidence 75/100Explain Gaussian Mixture Models and their assumptions.ML Fundamentals · medium · Evidence 75/100When would you prefer gradient descent to the normal equation?ML Fundamentals · medium · Evidence 75/100Explain BERT and its pretraining objectives.GenAI & LLM · medium · Evidence 75/100Explain Transformers in an NLP context.GenAI & LLM · medium · Evidence 75/100Compare major LLM fine-tuning techniques.GenAI & LLM · hard · Evidence 75/100How would you evaluate an LLM?GenAI & LLM · medium · Evidence 75/100How would you design an experiment when confounding is a concern?ML Fundamentals · hard · Evidence 75/100What is the closed-form solution for linear regression?ML Math · medium · Evidence 75/100How can Transformers be used in recommendation systems?GenAI & LLM · hard · Evidence 75/100Analyze the space complexity of major Transformer components.GenAI & LLM · hard · Evidence 75/100Design a RAG system that generates presentation slides from a user prompt.GenAI & LLM · hard · Evidence 75/100What RAG projects have you built?Project & Behavioral · medium · Evidence 75/100How would you forecast daily grocery inventory for the next week?ML System Design · medium · Evidence 75/100Explain how RAG works end to end.GenAI & LLM · medium · Evidence 75/100Describe a hard technical challenge from an ML project.Project & Behavioral · medium · Evidence 75/100