Power BI Interview Questions for 5 Years Experience
40 questions with answers for candidates with 5 years of experience — 1 easy, 19 medium, 20 hard.
What interviewers expect: 5 years experience
At five years, interviews test solution architecture: shared semantic models, workspace strategy, capacity planning, governance, aggregations and Dual mode, and Git-based development with PBIP. You are expected to review others' work, mentor juniors and manage stakeholders. Expect questions on how you standardised reporting or consolidated duplicate models in a past role.
This set is weighted towards Performance Optimisation and Administration (8), Advanced DAX and Time Intelligence (7), Power Query and Data Transformation (6), Power BI Service, Sharing and Security (6).
Shared model strategy Governance and security Aggregations and composite models Mentoring and reviews
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01
Users need to filter a report by 5,000 product names using a slicer, and it is slow. What do you do?
A slicer with thousands of values sends heavy queries and is hard to use. I would add a hierarchy so users pick category and subcategory first, enable the slicer search box, and consider a text filter visual for direct search. Apply buttons in query reduction settings stop queries on every click. If the slicer depends on a measure-filtered list, I would simplify that logic.
02
Write an M query that filters rows, removes columns and changes types.
let
Source = Sql.Database("server", "SalesDB"),
Orders = Source{[Schema="dbo", Item="Orders"]}[Data],
Filtered = Table.SelectRows(Orders, each [OrderDate] >= #date(2024, 1, 1)),
Kept = Table.SelectColumns(Filtered, {"OrderID", "OrderDate", "CustomerID", "Amount"}),
Typed = Table.TransformColumnTypes(Kept, {{"Amount", Currency.Type}, {"OrderDate", type date}})
in
Typed
All these steps fold to SQL on a database source.
03
A source table has duplicate customer rows with different spellings of the same name. What do you do?
For exact duplicates, Remove Duplicates on the key column. For spelling variations, use fuzzy matching in Merge Queries with a similarity threshold and transformation table, review results, and maintain a mapping table of approved matches. The best long-term fix is to use a stable customer ID from the source system and report data quality issues to the owner rather than cleaning endlessly in Power BI.
Calculation groups are reusable sets of calculation items that modify any measure, such as Current, YTD, Previous Year and YoY %, using SELECTEDMEASURE(). Instead of writing YTD versions of 30 measures, you write one item that applies to all. They can be created in Power BI Desktop model view or Tabular Editor. They reduce measure sprawl but change how measures behave, so naming and format strings need care.
05
A colleague's measure uses FILTER(Sales, ...) on a 50-million-row table and is slow. How would you rewrite it?
I would replace FILTER over the whole fact table with column filters in CALCULATE, such as CALCULATE([Sales], Sales[Channel] = "Online"), which the engine can apply efficiently. If a condition uses a measure, iterate over a small dimension table instead, like FILTER(VALUES(Customer[CustomerID]), [Sales] > 10000). Then test in DAX Studio with server timings before and after.
Key table functions include FILTER, ALL, VALUES, DISTINCT, SUMMARIZE and SUMMARIZECOLUMNS for grouping, ADDCOLUMNS to add calculated columns, TOPN for top rows, CROSSJOIN, UNION, EXCEPT, INTERSECT, GENERATESERIES and TREATAS for virtual relationships. They return tables used inside iterators, CALCULATE filters or calculated tables. ADDCOLUMNS over SUMMARIZE is a common pattern for reliable grouped results.
07
Reports slow down every morning at 9 a.m. on shared capacity. What could be happening?
Morning peaks often combine many users opening reports with heavy scheduled refreshes running at the same time. I would check the Fabric Capacity Metrics app for throttling and identify the heaviest items. Fixes include moving refreshes to off-peak hours, optimising the largest semantic models, spreading workloads across capacities, or scaling the capacity. Communicating refresh windows to teams also helps.
Power BI Project (PBIP) saves a report and model as folders of text files instead of one binary PBIX file. The semantic model is stored in TMDL or TMSL and the report in JSON definitions. This makes Git version control, code reviews, diffs and merge of changes practical, and works with Fabric Git integration and deployment pipelines. It is preferred for team development and CI/CD.
09
Users on mobile find the report hard to read. What do you do?
I would create a mobile layout in Desktop through View, Mobile layout, placing the most important cards and charts in a single column with larger fonts. Remove or simplify dense tables, check slicer usability on touch screens and test in the Power BI mobile app. If mobile use is common, I might design a separate concise summary page for mobile users.
10
Managers want to see the top 5 products plus an 'Others' row that sums the rest. How do you build it?
I would create a calculated table of product names plus an Others row, related or disconnected, and a measure that ranks products with RANKX over ALL products. For rows ranked 1 to 5 it returns their sales; for Others it returns total sales minus the top 5. TOPN helps compute the top 5 total. The rank should respect slicers like year so the top 5 updates dynamically.
11
How do you configure incremental refresh on a sales table?
In Power Query create RangeStart and RangeEnd parameters of type Date/Time, and filter OrderDate so it is greater than or equal to RangeStart and less than RangeEnd. Confirm the step folds to the source. In Desktop right-click the table, choose Incremental refresh, set to archive, say, 5 years and refresh the last 10 days, optionally detect data changes. Publish, and the Service creates partitions on first refresh.
VAR defines a named value inside an expression and RETURN gives the final result. Variables make measures easier to read, avoid repeating the same calculation, which improves performance, and help debugging because you can return an intermediate variable. A variable is evaluated once in the context where it is defined, so its value does not change if later CALCULATE filters are applied.
13
A report page takes 25 seconds to load. Walk me through how you would fix it.
I would run Performance Analyzer to find the slowest visuals, copy their DAX queries into DAX Studio and check server timings. Common fixes are rewriting measures that iterate large fact tables, removing bi-directional relationships, reducing visuals on the page, and shrinking the model by removing high-cardinality columns. If the source is DirectQuery, I would add aggregations or move to Import. Then re-measure after each change.
14
Tell me about a time you found a wrong number in a published report.
Situation: a regional head noticed our margin report did not match finance. Task: find and fix it quickly. Action: I compared numbers at product level, found returns were double-subtracted because a measure used both a net amount column and a returns table. I fixed the measure, added a reconciliation page against finance totals and informed users. Result: numbers matched to the rupee and the reconciliation check became standard.
let
StartDate = #date(2022, 1, 1),
EndDate = #date(2026, 12, 31),
Days = Duration.Days(EndDate - StartDate) + 1,
Dates = List.Dates(StartDate, Days, #duration(1, 0, 0, 0)),
T = Table.FromList(Dates, Splitter.SplitByNothing(), {"Date"}),
Typed = Table.TransformColumnTypes(T, {{"Date", type date}}),
Y = Table.AddColumn(Typed, "Year", each Date.Year([Date]), Int64.Type),
M = Table.AddColumn(Y, "Month", each Date.MonthName([Date]), type text)
in
M
16
What are the privacy levels in Power Query and why do they cause errors?
Privacy levels, Private, Organizational and Public, control whether data from one source can be sent to another source during combining, to avoid leaking sensitive data. When a query mixes sources with incompatible levels, Power Query may block it with a Formula.Firewall error or stop folding. The fix is to set correct privacy levels for each source or restructure queries so sources are combined in a staged way.
17
Totals look inflated after adding a second fact table. What could be wrong?
Likely a relationship is joining at the wrong grain or creating a many-to-many path, so rows get duplicated in filtering, or a bi-directional relationship is letting one fact filter another unexpectedly. I would check the relationships, keys and cardinality, make filters flow from shared dimensions only, and verify a measure against a known total in the source system using a simple table visual.
18
Tell me about a time you improved the performance of a slow report.
Situation: a sales report on DirectQuery took over 30 seconds per page and users had stopped opening it. Task: get pages under 5 seconds. Action: I added an Import aggregation table at day and store level, set dimensions to Dual, reduced the main page from 18 to 9 visuals and rewrote two FILTER-heavy measures. Result: page load fell to about 3 seconds and weekly active users doubled.
19
How do you control how visuals interact with each other?
By default, selecting a data point cross-filters or cross-highlights other visuals on the page. Use Format, Edit interactions to choose filter, highlight or none for each visual pair, for example stopping a slicer from affecting a target KPI card. Slicers can also be synced across pages with the Sync slicers pane. Clear interaction design prevents confusing behaviour.
Deployment pipelines move content through stages, typically Development, Test and Production workspaces. Creators deploy reports and semantic models from one stage to the next, compare differences, and use deployment rules to change data source connections or parameters for each stage. This supports controlled releases and testing before users see changes. They work alongside Git integration for version control in Fabric workspaces.
21
Scheduled refresh fails every night with a gateway error. How do you troubleshoot?
I would check the refresh history error details, confirm the gateway machine is on and the gateway service is running and updated, and verify data source credentials in the gateway connection have not expired. Then test connectivity from the gateway machine to the source and check that the source names in the model exactly match the gateway data source. Gateway logs and network or firewall changes are next.
Sales 3M Avg =
VAR periods =
DATESINPERIOD('Date'[Date], MAX('Date'[Date]), -3, MONTH)
RETURN
CALCULATE(
AVERAGEX(VALUES('Date'[Month Year]), [Total Sales]),
periods
)
AVERAGEX over months averages monthly totals instead of daily values. Month Year must be a column in the date table.
23
Describe how you would review another developer's Power BI model before release.
I check the model diagram for a clean star schema and single-direction relationships, run Best Practice Analyzer, and review VertiPaq Analyzer for oversized columns. I read key measures for correctness and naming, check that keys are hidden and formats set, test RLS roles, and run Performance Analyzer on main pages. I share findings as a short prioritised list, explaining why each change matters.
24
Your measure using IF and many nested CALCULATE calls is slow. How do you optimise it?
I would store repeated sub-expressions in variables so they are computed once, replace nested IF chains with SWITCH(TRUE(), ...), use column filters instead of FILTER over tables, and avoid context transition inside large iterators. I would also check whether some logic can move into a calculated column or Power Query at refresh time. DAX Studio timings confirm whether formula engine time drops.
25
Thirty measures each need YTD, previous year and YoY versions. How do you avoid 120 measures?
I would create a calculation group, such as Time Calculation, with items Current, YTD, PY and YoY % that use SELECTEDMEASURE() wrapped in the time intelligence logic, and set format strings for percent items. Users pick the item from a slicer or matrix columns. This keeps the model small and consistent. I would document it because calculation groups change measure behaviour everywhere.
26
What are slowly changing dimensions and how do they affect Power BI models?
Slowly changing dimensions track attribute changes over time. Type 1 overwrites the old value, so history shows the current attribute. Type 2 adds a new row with a surrogate key and valid-from and valid-to dates, preserving history, such as a customer moving region. In Power BI, Type 2 needs facts to carry the surrogate key, and the warehouse should handle it rather than Power Query.
27
What is Microsoft Fabric capacity and how do capacity units work?
Fabric capacity is a pool of compute purchased as F SKUs, from F2 upward, measured in capacity units that all workloads share, including Power BI semantic models, refreshes, notebooks and pipelines. Usage is smoothed over time, so short spikes are allowed, but sustained overuse causes throttling where interactive queries are delayed or rejected. Admins use the Fabric Capacity Metrics app to monitor and plan sizing.
28
Tell me about a time you handled a data access or security issue.
Situation: a sales user reported seeing another region's numbers after a reorganisation. Task: fix the leak fast. Action: I confirmed the security mapping table had stale entries, removed the user from the wrong row, refreshed the model and then automated the mapping from the HR system with a daily refresh. I informed the data owner. Result: access stayed correct after later reorganisations, and quarterly access reviews were added.
29
A DirectQuery report is slow and the database team complains about load. What do you do?
I would check which queries are slow using Performance Analyzer and the database's query logs. Then reduce visuals per page, add Import-mode aggregation tables for common summary views, set dimensions to Dual mode, and apply query reduction options so slicers send queries only on Apply. On the source side, indexes or columnstore tables help. If real-time is not essential, moving to Import with frequent refresh may be simpler.
30
A refresh fails with 'column not found' after the source team renamed a column. How do you make queries more robust?
I would fix the immediate step, then reduce dependence on exact column names: avoid hard-coded Changed Type steps on all columns, select only needed columns with MissingField.Ignore where suitable, and standardise names in one place. I would agree a data contract or SQL view with the source team so renames go through a stable interface, and set up refresh failure notifications.
31
How do you set up an app with different audiences?
In the workspace choose Create app or Update app, add the reports and dashboards, then in the Audience tab create audiences such as Sales Managers and Finance, choose which content each audience sees and grant access to the right Entra ID security groups. Publish the app and share the link. Remember RLS still controls rows inside reports; audiences only control which items are visible.
32
What is a decomposition tree and when is it useful?
The decomposition tree is an AI visual that lets users break down a measure across several dimensions in any order, for example splitting a sales drop by region, then category, then channel. It can also suggest the next split automatically using high value or low value analysis. It is useful for root-cause exploration by business users, though it is less suited to fixed reporting.
Bookmarks capture the current state of a report page, including filters, slicers, visual visibility and sort order. They are used for storytelling, toggling between chart and table views with buttons, creating custom navigation, and resetting filters. Combined with the selection pane, they show and hide visuals. Too many bookmarks become hard to maintain, so field parameters are often a simpler alternative for switching measures.
34
What is the difference between Group By in Power Query and summarising in DAX?
Group By in Power Query aggregates rows at refresh time and stores only the summarised table, reducing model size, which is useful when detail is never needed. Summarising in DAX through measures keeps detail in the model and aggregates dynamically for any filter at query time. Use Power Query grouping for fixed summaries such as monthly snapshots, and DAX measures when users need flexible slicing.
Field parameters let report users switch which measure or dimension a visual shows using a slicer, for example choosing between Sales, Profit and Units, or switching the axis between Region and Category. They are created through Modeling, New parameter, Fields, which generates a calculated table. They reduce the number of duplicate visuals and bookmarks needed for dynamic reports.
36
A report must be embedded in a customer-facing web portal for users without Power BI licences. What approach do you take?
I would use Power BI Embedded with the 'embed for your customers' pattern, also called app owns data. The application authenticates with a service principal, generates embed tokens and passes customer identity for RLS, so each customer sees only their data. It needs Fabric or embedded capacity. I would design RLS carefully, test token expiry and monitor capacity load as the customer base grows.
37
When would you use a custom visual and what are the risks?
Custom visuals from AppSource add chart types not built in, such as Gantt charts, sankey diagrams or advanced KPI cards. Risks include performance issues, limited support, export and accessibility gaps, and data security, since some visuals may call external services. Prefer certified visuals, check organisational policy, since admins can restrict them, and use built-in visuals where they meet the need.
38
How do you handle a many-to-many relationship between sales and budget at different grains?
Budgets are often at month and category level while sales are daily and per product. Instead of a direct many-to-many link, relate both fact tables to shared dimensions at the right level: Date and a Category dimension. Budget relates to Category and to Date through a month-level key or the first day of month. Measures then compare them, and visuals should use only the shared grain.
39
Tell me about the most complex DAX problem you solved.
Situation: finance needed month-end inventory balances, which are semi-additive and must not be summed across months. Task: build balances that work at any date level. Action: I wrote a measure using LASTNONBLANK over dates to take the closing balance per period and SUMX across warehouses, then validated against ERP reports for six months. Result: the report replaced a manual Excel process and matched ERP within rounding.
Context transition happens when CALCULATE, or a measure reference which implicitly wraps CALCULATE, is evaluated inside a row context. The values of the current row are converted into filters on the model. For example, in a calculated column on Customer, [Total Sales] returns that customer's sales because the row becomes a filter. It is powerful but can be slow over large tables and surprising with duplicate rows.
Frequently asked questions
What is asked in Power BI interviews for 5 years of experience?
At five years, interviews test solution architecture: shared semantic models, workspace strategy, capacity planning, governance, aggregations and Dual mode, and Git-based development with PBIP. You are expected to review others' work, mentor juniors and manage stakeholders. Expect questions on how you standardised reporting or consolidated duplicate models in a past role.
How many questions should I practise before a Power BI interview?
Work through all 40 questions here, then the company-wise sets for the employers you are targeting. Quality matters more than count: be able to explain why each answer is right.
Which topics matter most for 5 years of experience?
Focus first on Shared model strategy, Governance and security, Aggregations and composite models, Mentoring and reviews.