Business Intelligence Developer interview questions and how to answer them
BI developer interviews are less about pretty dashboards and more about whether your numbers survive contact with finance. Expect a live SQL exercise, a modeling whiteboard, and at least one story about a load that broke. Here's what they're really listening for.
What happens in each round
- 1
Recruiter screen
What happens
Whether your stack matches theirs. They'll ask which tools you've used in production, so be ready to say plainly whether it was SQL Server and SSIS, Snowflake and dbt, or Power BI on top of something else.
- 2
Technical SQL exercise
What happens
Whether you can write joins, window functions and aggregations correctly under light pressure, and whether you check your row counts before you trust a result.
- 3
Data modeling and design session
What happens
Whether you can take a messy business process, like orders and returns, and turn it into facts and dimensions at the right grain while talking through your choices.
- 4
Hiring manager and team conversation
What happens
How you handle failed refreshes, vague requests and stakeholders who want the same report rebuilt again. They're deciding if they'd trust you with production.
Questions you're likely to get
1.Walk me through how you'd design a star schema for sales orders.
Why they ask
Dimensional modeling is the core of the job, and this shows whether you think about grain before you think about columns.
How to answer
- State the grain first, such as one row per order line, and explain why that level
- Name the dimensions: date, customer, product, store or channel, and how they join through surrogate keys
- List the measures on the fact table and flag which ones are additive and which aren't, like unit price
- Say how returns and cancellations would be handled, either as negative rows or a separate fact
2.How do you handle a customer who changes address when your reports need history?
Why they ask
It's the classic slowly changing dimension test, and plenty of candidates know the term without having built one.
How to answer
- Explain the difference between overwriting the value and keeping history with a new row
- Describe a history-keeping setup with effective-from and effective-to dates and a current-row flag
- Mention how the fact table picks up the right version through the surrogate key at load time
- Say when you'd choose to just overwrite, because not every attribute deserves history
3.Your overnight load failed and the sales dashboard is showing yesterday's data. What do you do?
Why they ask
Every BI developer gets this morning eventually. They want to know you stay calm, communicate and fix the cause, not just the symptom.
How to answer
- Tell the affected users quickly that data is stale and when you expect a fix
- Check the job history in SQL Server Agent, Data Factory or the scheduler to find the failing step
- Fix and rerun safely, making sure the load is idempotent so a rerun doesn't double rows
- Add an alert or a data check so the same failure gets caught earlier next time
4.A Power BI report takes ages to load. How would you speed it up?
Why they ask
Slow reports are the most common complaint a BI team gets, and fixing them shows you understand the model underneath.
How to answer
- Start with Performance Analyzer to see whether the visuals, the DAX or the query is the slow part
- Check the model: remove unused columns, reduce high-cardinality text fields, and keep it a clean star
- Rewrite heavy DAX measures, often by replacing row-by-row iterators with simpler aggregations
- Consider import versus DirectQuery, aggregations tables and incremental refresh
5.Explain the difference between a calculated column and a measure in DAX.
Why they ask
It's a quick filter for people who've only dragged fields around versus people who've built models others rely on.
How to answer
- A calculated column is computed at refresh, stored in the model and evaluated row by row
- A measure is computed at query time and responds to filter context from slicers and visuals
- Give an example of each, like a customer age band column and a year-to-date revenue measure
- Mention that too many calculated columns bloat the model, so measures are usually the default
6.How would you load a large table incrementally instead of truncating and reloading it?
Why they ask
Full reloads work fine until the table grows, and they want to see you've dealt with that growth.
How to answer
- Pick a reliable change marker, like a modified timestamp, a rowversion column or change data capture
- Store a watermark of the last successful load and pull only newer rows
- Use a merge or upsert pattern to insert new rows and update changed ones
- Explain how you'd catch deletes and late-arriving records, and when a periodic full reload still makes sense
7.How do you set up row-level security so managers only see their own region?
Why they ask
Security mistakes in BI leak salary, margin and customer data, so they want someone careful here.
How to answer
- Describe a security table mapping user emails to regions, related to the region dimension
- Explain a dynamic role using the signed-in user's identity rather than one role per region
- Test it with the view-as feature before publishing
- Mention that workspace permissions and sharing can bypass RLS if you're careless
8.Write a query that returns each customer's most recent order.
Why they ask
It checks window functions and whether you think about ties and duplicates.
How to answer
- Use ROW_NUMBER partitioned by customer and ordered by order date descending
- Filter to the first row in an outer query or common table expression
- Point out what happens with two orders on the same timestamp and how you'd break the tie
- Mention checking the row count against the distinct customer count
9.Tell me about a time your numbers didn't match another team's report.
Why they ask
Reconciliation is half the job, and they want to know you dig instead of defending your number.
How to answer
- Name the specific mismatch and which systems were involved
- Walk through how you traced it, such as comparing filters, date logic or currency handling
- Say who was actually right and what definition got agreed
- Explain what you changed so it wouldn't happen again, like a shared measure or documentation
10.How do you manage changes to reports and models across dev, test and production?
Why they ask
Teams that edit production directly break things, and they want to know you've worked with some discipline.
How to answer
- Describe source control, such as Git with Power BI project files or SQL database projects
- Explain deployment pipelines or a release process that promotes work between environments
- Mention parameterized connections so the same model points at the right database per stage
- Say how you'd roll back if a release broke a report
11.A stakeholder asks for a new report that looks almost identical to an existing one. How do you respond?
Why they ask
Report sprawl kills BI teams slowly, and they want someone who can push back politely.
How to answer
- Ask what decision the new report is meant to support
- Show them the existing report and whether a filter, bookmark or extra measure covers it
- Build only what's genuinely new, ideally on the shared model
- Keep a note of the request so patterns in what people ask for shape the roadmap
Mistakes that sink good candidates
Talking only about visuals and colors when they asked about the model underneath
Claiming expertise in every tool on the posting, then stalling on a basic DAX or SQL follow-up
Blaming source systems or other teams for every data problem in your stories
Skipping the step where you check row counts or totals in the live SQL exercise
Need more Business Intelligence Developer interviews to prep for?
HeroApply applies to Business Intelligence Developer jobs that match you, every day. 73 jobs are open today.