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Practice real interview questions for Data Science, Machine Learning, and AI Engineering roles. Simulate interviews with AI, and build portfolio projects that prove you can reason like the job requires.
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SELECT candidate, role, offer FROM interviews WHERE track = 'Data Science' AND outcome = 'Offer'; -- 750,000+ rows and counting
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Everything You Need to Succeed
From practice questions to portfolio projects — for Data Science, Machine Learning, and AI Engineering interviews.
Interview Questions
1000+ real coding and concept questions for Data Science, ML, and AI Engineering interviews. SQL, Python, ML system design, statistics, and more.
Explore interview questionsAI InterviewerMock Interviews
AI-powered mock interviews for Data Scientist, ML Engineer, and AI Engineer roles — timed sessions with detailed feedback on code and communication.
Explore mock interviewsCloud NotebooksData Labs
Real take-home projects — including ML and AI engineering assignments — powered by our cloud hosted Python notebooks. No setup required.
Explore Data LabsFreeLearning Paths
Free comprehensive SQL and Python paths — the foundations every data and AI interview builds on. 6 modules, 36 lessons, and 160+ questions each.
Explore learning pathsBenchmarkingPerformance Insights
Track your skills, benchmark against the community, and build your public data profile.
Explore performance insightsRun & ValidateAI StrataTools
Validate and optimize your code in real environments — for Python, SQL, and applied ML workflows.
Explore AI StrataToolsNewAI Engineering Prep
ML system design, modeling, and take-home projects for AI Engineer and Machine Learning Engineer interviews — filtered to the role you are targeting.
Explore AI Engineering prepBuilt for the AI Engineering Interview Loop
Machine Learning Engineer and AI Engineer interviews go beyond SQL and Leetcode-style questions. Filter every question, project, and mock interview by the role you are targeting — AI Engineer, Machine Learning Engineer, Applied Scientist, MLOps Engineer, and more.
ML System Design & Modeling
350+ concept questions filtered to AI and ML roles — system design, modeling, statistics, and probability. Submit an answer and the AI Evaluator scores it on completeness, accuracy, depth, and structure.
Practice AI Engineer concept questionsTake-home roundML Take-Home Projects
60+ real take-home assignments tagged for AI and ML roles, in cloud-hosted Python notebooks. No local setup — build the project and share it straight from your Performance page.
Browse ML take-home projectsInterview roundRole-Targeted Mock Interviews
Run a timed mock interview for the exact role you are targeting — AI Engineer, Machine Learning Engineer, or Data Scientist — with detailed feedback on your code and communication.
Start an AI Engineer mock interviewSimulate Real Interviews Before the Real Thing
Practice under real conditions with an AI interviewer that tracks your time and delivers detailed feedback — for Data Scientist, ML Engineer, and AI Engineer interview loops.
- →Choose your role, company, and difficulty — or Quick Start instantly
- →Detailed scoring on code quality, correctness, and communication
- →Personalized AI review with actionable feedback on your reasoning
SMS Confirmations by FB
Find the number of phone numbers that were sent a confirmation SMS text by carrier on August 7, 2020…
Build Real Data & AI Projects in Our Cloud-Hosted Notebooks
Practice real take-home assignments — including ML and AI engineering assignments — from top companies. Build your portfolio and share it straight from your Performance page. No local setup required.
Structured Learning Paths for SQL & Python
Go from foundations to interview-ready with our comprehensive free learning paths — the same foundations that underpin Data Science, ML, and AI Engineering interviews.
Comprehensive SQL
Master SQL from foundations to advanced window functions. 6 modules covering everything you need for data and ML interviews.
- 01SQL Foundations4 hr 30 min
- 02Aggregating & Grouping Data3 hr 25 min
- 03Working with Multiple Tables4 hr 5 min
- 04Subqueries & CTEs2 hr 20 min
- 05Date, Time & Text Functions3 hr 20 min
- 06Window Functions2 hr 55 min
Comprehensive Python
Pandas, data wrangling, and interview patterns that carry straight into ML and AI engineering take-homes.
- 01Python Foundations4 hr 10 min
- 02Pandas Fundamentals3 hr 40 min
- 03Data Wrangling4 hr 0 min
- 04Aggregations & Group Operations2 hr 50 min
- 05Statistics with Python3 hr 15 min
- 06Interview Patterns3 hr 30 min
AI StrataTools Run Your Code — So You Don't Run Into Errors
Validate and optimize your Python and SQL by running it in real environments, reducing AI hallucinations for both data and applied ML workflows.
Loved by Data & AI Professionals
Join thousands who landed jobs as Data Scientists, ML Engineers, and AI Engineers at top tech companies
“StrataScratch has been super helpful. I started with barely being able to finish an easy SQL query to no problem solving most of the medium level in just a few days.”
Kyle
Twitch
“StrataScratch is hands down the best platform if you are preparing for or am working as a data analyst/scientist/engineer. Happy to share that I have gotten an offer from Amazon as a Data Analyst.”
Triman
Amazon
“I really wanted to get into data analytics and data science but never really understood the importance of SQL. The questions are really very realistic and I was asked similar questions in my coding rounds.”
Hemant R
Credit Karma
“SQL is something that is super important and plays a key role in Data Analysis. I used to practice 2-3 SQL problems everyday. The discussion forum and solution with clear understanding cleared my barriers.”
Vikram
Microsoft
“StrataScratch and the community really helped me prep for the interview — I ended up getting the Data Scientist internship!”
Joe
Microsoft
“StrataScratch is awesome! It's the first place I found that allows you to use python in addition to SQL. The Facebook questions were quite similar to the ones that I saw in my interview today.”
Ryan
Level Up Your Data Skills
From SQL fundamentals to AI-era interview prep — free guides, tutorials, and resources from our team
How SQL EXISTS Works and When to Use It
Ignore EXISTS at your own peril! Learn how SQL EXISTS actually works, how it compares to IN and JOIN, and solve actual interview questions.
Tihomir Babic -
SQL Execution Order Explained With Real Query Examples
SQL execution order decides how queries actually run. Learn why FROM comes first, how aliases fail in WHERE, and when to use HAVING, with real examples.
Sara Nobrega -
Your Next Data or AI Interview Is Closer Than You Think
Start practicing real Data Science, ML, and AI Engineering interview questions today. No credit card required.