Tech Lessons
Structured courses for coding, system design, machine learning and GenAI, data science and behavioral rounds. Each one moves from a clear mental model to worked examples and interview practice.
New here? Start with
- Practical PythonBeginner · 35 hours · 3 free lessons
- Foundations of System DesignBeginner · 18 hours · 4 free lessons
- Machine Learning Interview PlaybookIntermediate · 18 hours · 9 free lessons
Every course opens with free lessons.
- Courses
- 14
- Lessons
- 794
- Hours of study
- 288
- Free lessons
- 73
Software Engineering
5 courses386 lessons91 hoursBuild coding fluency, then move from reliable services to senior architecture trade-offs.
- Coding practice
Blind 75
75 coding problems. Examples, hints, and solution approaches. Build the foundations and track your progress.
- Arrays
- Graphs
- Dynamic programming
75 problemsFree collection - Coding practice
Coding & Algorithms
Practice interview coding questions by topic, from arrays and linked lists to trees, graphs, and dynamic programming.
- Arrays
- Trees
- Dynamic programming
982 problemsQuestion bank - Start hereRated 4.8 out of 5 from 9 ratingsBeginner
Practical Python: Foundations, Patterns, and Problem Solving
Learn Python by tracing programs, choosing data structures, and solving exercises in an editable console. Build from values and control flow to functions, collections, classes, packages, and two checkpoints that combine these ideas.
- Python fluency
- Problem solving
- Interactive practice
35 hours90 lessons3 free lessons - Core conceptsRated 5.0 out of 5 from 29 ratingsBeginner
Foundations of System Design
Develop a system design from requirements and runtime fundamentals through networks, coordination, storage, security, and scaling. Worked examples and practice questions connect each design choice to its assumptions, costs, and failure behavior.
- Requirements
- Networking and APIs
- Consistency and failures
18 hours40 lessons4 free lessons - Interview casesRated 5.0 out of 5 from 50 ratingsAdvanced
System Design Interview Casebook
Learn system design through detailed building blocks, worked interview cases, and a separate crash review path. Practice capacity estimates, data correctness, failure recovery, and clear explanations of design trade-offs.
- Building blocks
- Interview cases
- Capacity estimates
38 hours256 lessons9 free lessons
Machine Learning & AI
5 courses320 lessons116 hoursMove from model judgment to production ML, foundation models, GenAI platforms, and agents.
- Applied MLRated 4.8 out of 5 from 11 ratingsIntermediate
Machine Learning Interview Playbook: Practical Systems and Case Studies
Practice the decisions that come up in machine learning interviews: framing a task, choosing a baseline, evaluating models, debugging failures, and explaining project work with evidence.
- Problem framing
- Ranking and recommendation
- Model evaluation
18 hours74 lessons9 free lessons - LLM foundationsRated 4.8 out of 5 from 12 ratingsIntermediate
How Large Language Models Work: Foundations, Training, and Applications
Follow text through a language model, then study how training, retrieval, tools, and evaluation shape an application. Numerical examples and text, image, audio, and video cases connect model mechanics with system design decisions.
- Transformer internals
- Training and alignment
- RAG and tools
20 hours53 lessons2 free lessons - ML system designRated 4.9 out of 5 from 29 ratingsAdvanced
Machine Learning System Design Interview: Frameworks and Casebook
Design machine learning systems that connect product decisions to labels, features, training, serving, experiments, monitoring, and recovery, then apply the method to realistic interview cases.
- Data and features
- Training and serving
- Experimentation
27 hours102 lessons6 free lessons - GenAI systemsRated 4.9 out of 5 from 28 ratingsAdvanced
Designing Generative AI Systems: Architecture, Scale, and Deployment
Design generative AI services around explicit requirements, authorized retrieval, capacity estimates, evaluation, safety checks, and reversible releases. Text, image, speech, video, and captioning cases show how the tradeoffs change by workload.
- RAG and fine-tuning
- Inference optimization
- Capacity estimates
22 hours42 lessons4 free lessons - AI agentsRated 4.7 out of 5 from 11 ratingsAdvanced
Designing Reliable AI Agents: Architecture, Control, and Evaluation
Design agents that use narrow tools, preserve durable state, stop on clear conditions, and act only within granted authority. The course covers retries, approvals, sandboxing, evaluation, incident stops, and the cases where a fixed workflow is the better design.
- Agent architecture
- Tool permissions
- Evaluation
29 hours49 lessons6 free lessons
Data Science
3 courses58 lessons68 hoursPractice product decisions, experiments, and complete take-home analyses.
- Product judgmentRated 4.7 out of 5 from 11 ratingsAdvanced
Product Data Science
Practice product data science through metrics, experiments, model interpretation, and SQL. Worked examples show how to check assumptions, explain uncertainty, and connect an analysis to a product decision.
- Product sense
- Metric design
- Experimentation
26 hours26 lessons9 free lessons - ExperimentationRated 4.8 out of 5 from 9 ratingsIntermediate
A/B Testing for Data Science Interviews: From Framing to Final Decision
This course is designed to help Data Scientists systematically master A/B testing interview questions, from high-level product reasoning to rigorous statistical analysis. A/B testing questions are among the most common and most discriminating interview questions for product, growth, marketplace, and ML-adjacent Data Science roles. Interviewers are not only evaluating statistical knowledge, but also: Whether you can frame ambiguous problems Whether you understand causality and experimental design Whether you can reason about bias, dilution, power, and trade-offs Whether you can translate results into clear product decisions This course teaches a single, reusable mental framework that allows you to answer any A/B testing question with structure, confidence, and depth. What This Course Emphasizes Interview-ready answer structures Both math/statistics and product reasoning Real-world experimentation pitfalls interviewers care about Common follow-up questions and how to handle them Concrete examples from real interview questions Clear verbal phrasing you can use in live interviews
- Experiment framing
- Metric design
- Statistics
12 hours13 lessons2 free lessons - Applied practiceRated 4.6 out of 5 from 11 ratingsAdvanced
Data Science Projects
Work through data science projects with examples of data cleaning, exploration, modeling, and written recommendations. Use the solutions to compare assumptions and reasoning, then adapt the approach to the data and evaluation criteria in your own assignment.
- Take-home challenges
- End-to-end analysis
- Written recommendations
30 hours19 lessons14 free lessons
Interview Skills
1 course30 lessons13 hoursTurn real experience into specific, credible answers without sounding rehearsed.