Question bank

Interview questions, with guidance on how to answer

834 questions across 64 roles. Open one to see what a strong answer includes and common slips, then drill it out loud with Ava. New to answer structure? Start with the learning hub.

834 questions.

TechnicalEntry levelData Analyst
What's the difference between an inner join and a left join, and when could picking the wrong one give you misleading numbers?
Tests: SQL querying
TechnicalEntry levelData Analyst
You're handed a spreadsheet of sales with duplicate rows, mixed date formats and some blank regions. How would you clean it up?
Tests: Data cleaning & spreadsheets
TechnicalEntry levelData Analyst
How do you decide which kind of chart to use for a particular piece of data?
Tests: Visualisation & dashboards
TechnicalMid levelData Analyst
Weekly sign-ups dropped fifteen percent last week. Walk me through how you'd figure out why.
Tests: Analytical problem solving
TechnicalMid levelData Analyst
If you were asked to define the key metrics for a subscription business, which would you choose and why?
Tests: Metrics & business sense
TechnicalMid levelData Analyst
Tell me about a complex query you wrote, maybe using window functions or several steps. What problem did it solve?
Tests: SQL querying
BehaviouralMid levelData Analyst
Tell me about a time you turned an analysis into a clear recommendation that someone actually acted on.
Tests: Communication & storytelling
BehaviouralSeniorData Analyst
How would you move a team that constantly sends you ad hoc data requests toward answering more of their own questions?
Tests: Stakeholder management
TechnicalSeniorData Analyst
A marketing manager says a campaign worked because sales went up the month it ran. How would you test whether that's really true?
Tests: Basic statistics
System designSeniorData Analyst
How do you design a dashboard that executives will actually use, rather than one that gets ignored after a month?
Tests: Visualisation & dashboards
BehaviouralAny levelData Analyst
Tell me about a time someone questioned your numbers. How did you respond?
Tests: Stakeholder management
TechnicalAny levelData Analyst
How would you explain the difference between an average and a median to a colleague, and when does the median matter more?
Tests: Basic statistics
TechnicalEntry levelMachine Learning Engineer
Why do we split data into training, validation and test sets, and what goes wrong if information leaks between them?
Tests: Model training & evaluation
TechnicalEntry levelMachine Learning Engineer
How would you turn a notebook a data scientist gave you into code that's safe to run in production?
Tests: Software engineering practices
TechnicalEntry levelMachine Learning Engineer
What does it mean for features to be computed the same way in training and in production, and why does that matter?
Tests: Data & feature pipelines
TechnicalMid levelMachine Learning Engineer
Walk me through how you've deployed a model. How was it packaged, served and rolled out safely?
Tests: MLOps & deployment
BehaviouralMid levelMachine Learning Engineer
Tell me about a time a model's performance dropped in production. How did you notice and what did you do?
Tests: Model monitoring & reliability
TechnicalMid levelMachine Learning Engineer
Your model training takes twelve hours on a GPU and the team needs to iterate faster. What would you try?
Tests: Model training & evaluation
BehaviouralMid levelMachine Learning Engineer
Tell me about a time you disagreed with a data scientist or product manager about whether a model was ready to ship.
Tests: Cross-functional collaboration
System designSeniorMachine Learning Engineer
How would you design a recommendation system for an online store that needs to respond in under a hundred milliseconds?
Tests: ML system design