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Multi Armed Bandits and Experimentation Questions

Covers adaptive experimentation methods that trade off exploration and exploitation to optimize sequential decision making, and how they compare to traditional A B testing. Core concepts include the exploration versus exploitation dilemma, regret minimization, reward modeling, and handling delayed or noisy feedback. Familiar algorithms and families to understand are epsilon greedy, Upper Confidence Bound, Thompson sampling, and contextual bandit extensions that incorporate features or user context. Practical considerations include when to choose bandit approaches versus fixed randomized experiments, designing reward signals and metrics, dealing with non stationary environments and concept drift, safety and business constraints on exploration, offline evaluation and simulation, hyperparameter selection and tuning, deployment patterns for online learning, and reporting and interpretability of adaptive experiments. Applications include personalization, recommendation systems, online testing, dynamic pricing, and resource allocation.

HardSystem Design
32 practiced
Describe how to run randomized A/B tests and bandit-based experiments in parallel on the same product surface without invalidating inference. Discuss traffic splitting, user-level assignment, interference concerns, and analysis strategies to keep results interpretable.
EasyTechnical
45 practiced
Define contextual bandits and give two real-world product examples where context matters. For each example, list at least three contextual features you would include and why they might improve personalization.
MediumSystem Design
44 practiced
Design the logging schema and retention strategy for bandit experiments such that analysts can reproduce historic decisions, perform offline evaluation, and backfill delayed rewards. Include required fields, event joins, and a plan for handling schema evolution.
HardSystem Design
42 practiced
Design a production architecture for serving a contextual bandit across multiple regions with low-latency action selection, periodic model retraining, and strong auditability. Include components for feature store, online model server, offline training, logging, and a rollback mechanism for failed models.
EasyTechnical
69 practiced
As a data analyst, define regret in the context of multi-armed bandits. Given an arm reward sequence and a known optimal arm reward 0.6, explain how to compute cumulative regret for a sequence of observed rewards [0.4, 0, 0.6, 0.5]. Show the formula and one interpretation of the result for stakeholders.

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