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Power BI / BI Architect Interview Questions & Answers

40 questions for Power BI / BI Architect interviews — 1 easy, 15 medium, 24 hard.

About the Power BI / BI Architect role

BI Architects design the overall analytics platform: shared semantic models, workspace and capacity strategy, security, deployment pipelines, Git-based development and Fabric components like lakehouses and Direct Lake. They set standards for modelling, naming and performance, guide developer teams and work with data engineering and security teams. Interviews test architecture judgement, governance and large-scale performance tuning experience. Strong communication with leadership teams is also essential.

Fabric architecture Capacity planning Governance and security Performance tuning CI/CD for BI
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01

Business users keep asking for edits directly in production reports. How do you set up a better process?

Power BI Service, Sharing and SecurityMedium
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I would set up separate Development, Test and Production workspaces with a deployment pipeline, store PBIP files in Git, and route requests through a simple backlog. Changes are built in Dev, reviewed by a key user in Test and deployed to Production on a release schedule. Users consume through an app, so production stays stable and changes are traceable.
02

A business user asks to merge customer and sales into one table to make it easier. How do you respond?

Data ModellingEasy
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I would explain that a star schema with separate Customer and Sales tables is easier for them in practice: slicers are cleaner, totals are correct and reports run faster. To keep it user-friendly I would hide key columns, organise measures in display folders and name fields in plain language. I would show them the field list so they see simplicity on the surface.
03

How does the VertiPaq engine store and compress data?

Performance Optimisation and AdministrationMedium
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VertiPaq is the in-memory columnar engine for Import models. It stores each column separately and compresses it using dictionary encoding, which maps unique values to integers, value encoding for numbers, and run-length encoding for repeated sequences. Compression depends mostly on column cardinality, so columns with few unique values compress very well, while unique IDs and precise timestamps take most of the memory.
04

Users export large amounts of sensitive data from reports to Excel. How do you control it?

Power BI Service, Sharing and SecurityHard
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I would review whether export is really needed and adjust export settings per report or at tenant level, for example allowing only summarised data. I would apply Purview sensitivity labels so exported files keep protection, use RLS and OLS to limit what can be exported, and monitor exports through the activity log. For legitimate detailed needs, a governed paginated report is better.
05

What is the Dual storage mode?

Performance Optimisation and AdministrationHard
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Dual mode tables act as Import or DirectQuery depending on the query. In a composite model, dimension tables set to Dual can be served from memory when joined to Import aggregation tables, and sent to the source when joined to DirectQuery fact tables, avoiding slow cross-source joins. It is commonly used for dimensions in models that mix aggregations with DirectQuery detail.
06

What are aggregation tables and how do they improve performance?

Performance Optimisation and AdministrationHard
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Aggregation tables store pre-summarised data, such as sales by day, product and store, in Import mode, while detail stays in a large DirectQuery table. With Manage aggregations, Power BI automatically answers queries from the small aggregation when the requested grain allows it and falls back to detail otherwise. This gives fast summary visuals on billion-row data while still allowing drill to detail.
07

How do you use a bridge table for a many-to-many scenario?

Data ModellingHard
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For example, accounts can have multiple customers and customers multiple accounts. Create a bridge table with unique Account and Customer pairs. Relate Customer to Bridge one-to-many, and Account to Bridge one-to-many, with the Bridge to Account relationship set to filter in both directions or use CROSSFILTER in measures. Facts relate to Account. Test totals carefully because shared accounts count once per customer.
08

Tell me about a time you improved the performance of a slow report.

Performance Optimisation and AdministrationHard
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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.
09

A YTD measure returns blank for future months on a chart. Users want the line to stop at today. How?

Advanced DAX and Time IntelligenceMedium
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The issue is the opposite for many teams: YTD repeats the last value for future months. I would add a condition so the measure returns BLANK when the period starts after the last date with data, for example IF(MIN('Date'[Date]) > [Last Sales Date], BLANK(), TOTALYTD(...)). Alternatively add a column flagging dates up to today in the date table and filter the visual on it.
10

Managers want to see the top 5 products plus an 'Others' row that sums the rest. How do you build it?

Advanced DAX and Time IntelligenceHard
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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

What are calculation groups?

Advanced DAX and Time IntelligenceHard
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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.
12

Write a dynamic RLS rule using a security mapping table.

Power BI Service, Sharing and SecurityHard
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// Security table: Email, Region; related to Region[Region] // Role filter on Security table: [Email] = USERPRINCIPALNAME() // Optional all-access rule on Region table instead: VAR u = USERPRINCIPALNAME() RETURN LOOKUPVALUE(Security[Region], Security[Email], u) = "ALL" || Region[Region] IN CALCULATETABLE(VALUES(Security[Region]), Security[Email] = u)
13

Tell me about the most complex DAX problem you solved.

Advanced DAX and Time IntelligenceHard
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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.
14

Your model has one wide flat table with 80 columns from an Excel export. How would you remodel it?

Data ModellingMedium
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I would identify the grain, such as one row per order line, and split descriptive attributes into dimension tables like Customer, Product, Store and Date using Reference queries and Remove Duplicates on keys. The fact table keeps keys and numeric columns only. Then create one-to-many single-direction relationships. This reduces size, simplifies DAX and makes slicers faster and more reliable.
15

Thirty measures each need YTD, previous year and YoY versions. How do you avoid 120 measures?

Advanced DAX and Time IntelligenceHard
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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.
16

Reports slow down every morning at 9 a.m. on shared capacity. What could be happening?

Performance Optimisation and AdministrationHard
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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.
17

What is a calculated table and when would you use one?

Data ModellingMedium
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A calculated table is created with a DAX expression and stored in the model, recalculated at refresh. Examples are a date table using CALENDAR, a disconnected parameter table for what-if analysis, or a summary table. It is handy but adds memory, and it cannot use Power Query folding. For most shaping tasks, creating tables in the source or Power Query is preferred.
18

What is Microsoft Fabric capacity and how do capacity units work?

Performance Optimisation and AdministrationHard
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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.
19

Each regional manager must see only their region, and the CEO must see everything. How do you implement this?

Power BI Service, Sharing and SecurityMedium
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I would build dynamic RLS with a security table of Email and Region, related to the Region dimension, and a role filter Security[Email] = USERPRINCIPALNAME(). The CEO and other full-access users get an 'All' flag handled in the rule, or are placed in a separate role with no filter. I would test with View as role in Desktop and in the Service before publishing the app.
20

What does the XMLA endpoint allow you to do?

Power BI Service, Sharing and SecurityHard
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The XMLA endpoint exposes semantic models on Premium, PPU or Fabric capacity like an Analysis Services server. Tools such as Tabular Editor, DAX Studio, SQL Server Management Studio and ALM Toolkit can then read or write the model, manage partitions, refresh specific tables, script deployments and apply object-level security. Read-write mode must be enabled in capacity settings by an admin.
21

Tell me about a time you redesigned a data model.

Data ModellingMedium
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Situation: a finance report took 40 seconds per page with a 2 GB file built on joined flat tables. Task: improve speed. Action: I split it into a star schema with Date, Account, Cost Centre and fact tables, removed unused columns, turned off auto date/time and replaced bi-directional filters with single direction. Result: model size dropped to 450 MB and pages loaded in under 4 seconds.
22

What are slowly changing dimensions and how do they affect Power BI models?

Data ModellingHard
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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.
23

The model is 9 GB and refresh times out. What would you do?

Performance Optimisation and AdministrationHard
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I would analyse it with VertiPaq Analyzer to find the largest columns and tables, remove unused columns, split or round datetime columns, replace text keys with integer keys and drop history users do not need. Then set up incremental refresh on large fact tables so only recent partitions reload. If needed, push heavy transformations upstream into the warehouse and consider Direct Lake on Fabric.
24

Two queries return the same data from different systems, and totals do not match. How do you investigate?

Power Query and Data TransformationHard
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I would compare row counts and totals at a high level first, then drill down by date and key dimensions to find where the difference starts. Merge both tables with a full outer join on the business key and use anti joins to list missing rows, then compare values on matched rows. Common causes are different cut-off times, filters, duplicates, time zones or currency conversions.
25

Write a measure that counts new customers in a period.

Advanced DAX and Time IntelligenceHard
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New Customers = VAR minDate = MIN('Date'[Date]) RETURN COUNTROWS( FILTER( VALUES(Sales[CustomerID]), CALCULATE(MIN(Sales[OrderDate]), REMOVEFILTERS('Date')) >= minDate ) ) A customer is new if their first ever order falls in the current period.
26

What is the difference between ISFILTERED, ISINSCOPE and HASONEVALUE?

Advanced DAX and Time IntelligenceHard
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ISFILTERED returns true if a column has a direct filter. HASONEVALUE returns true when exactly one value is visible, useful before SELECTEDVALUE. ISINSCOPE returns true when a column is the current grouping level in a visual hierarchy, which is the most reliable way to detect subtotal versus detail rows in matrices. For example, IF(ISINSCOPE('Product'[Product]), [Sales], BLANK()) hides subtotals.
27

What are deployment pipelines?

Power BI Service, Sharing and SecurityMedium
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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.
28

Explain how RANKX works and common mistakes with it.

Advanced DAX and Time IntelligenceMedium
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RANKX iterates a table, evaluates an expression for each row and ranks the current value among them. A common pattern is RANKX(ALL('Product'[Product]), [Total Sales]). Mistakes include not using ALL, so every product ranks 1 because only one is visible, ranking over a table with duplicates, and forgetting ties handling with the Dense option. The newer RANK function supports multi-column ordering.
29

How do you configure incremental refresh on a sales table?

Power BI Service, Sharing and SecurityHard
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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.
30

What is the grain of a fact table and why does it matter?

Data ModellingMedium
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Grain is the level of detail of one fact row, such as one row per order line per day. It must be defined clearly before building measures, because mixing grains in one table, for example daily sales and monthly targets, causes double counting and wrong totals. Facts at different grains should be separate tables related to dimensions at the matching level.
31

What is object-level security?

Power BI Service, Sharing and SecurityHard
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Object-level security hides entire tables or columns from specific roles, so users in that role cannot see or query them, for example hiding a Salary column from non-HR users. It is configured with Tabular Editor or similar external tools on the model's roles. Unlike RLS, which filters rows, OLS removes metadata access. Visuals using a secured object show an error for restricted users.
32

A report must be embedded in a customer-facing web portal for users without Power BI licences. What approach do you take?

Power BI Service, Sharing and SecurityHard
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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.
33

What are surrogate keys and why are they used?

Data ModellingHard
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Surrogate keys are system-generated integer keys, such as ProductKey, used in dimensions instead of business keys like product codes. They handle changes in business keys, support Type 2 history with multiple rows per business key, and integer keys compress and join better in VertiPaq than long text keys. They are usually created in the data warehouse layer.
34

What are the formula engine and storage engine in Power BI?

Performance Optimisation and AdministrationHard
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The storage engine, VertiPaq or DirectQuery to the source, retrieves and aggregates data quickly and in parallel. The formula engine handles complex DAX logic that the storage engine cannot, working single-threaded on intermediate results. Fast measures push most work to the storage engine. DAX Studio's server timings show time spent in each, helping identify measures that create large intermediate data caches for the formula engine.
35

Scheduled refresh fails every night with a gateway error. How do you troubleshoot?

Power BI Service, Sharing and SecurityMedium
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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.
36

How do you mentor junior Power BI developers in your team?

Power BI Service, Sharing and SecurityMedium
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I pair with them on real tasks, review their models and DAX with clear reasons rather than just fixes, and share a short checklist covering star schema, naming, measures over columns and performance checks. I give them ownership of small reports early. One junior I mentored moved from building single-table reports to owning a shared finance model within six months.
37

A measure works in a card but gives wrong results in a matrix with subtotals. How do you debug it?

Advanced DAX and Time IntelligenceHard
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I would test the measure at each level of the matrix using a table visual and check how filter context differs at the subtotal. Often logic uses SELECTEDVALUE or MAX, which return blank or misleading results when several values are visible. I would use ISINSCOPE to branch logic or SUMX over the grouping column for additive results, and validate with DAX Studio queries.
38

What is a disconnected table and how is it used for what-if analysis?

Advanced DAX and Time IntelligenceMedium
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A disconnected table has no relationship to the model and is used to capture a user's choice through a slicer. For example, a Discount table from 0 to 30 percent created with GENERATESERIES, or the What-if parameter feature, lets a measure read SELECTEDVALUE(Discount[Value]) and calculate projected revenue. Since it does not filter facts, the measure decides how the selection is applied.
39

Describe how you would review another developer's Power BI model before release.

Performance Optimisation and AdministrationMedium
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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.
40

How do you run a DAX query in DAX Studio to test a measure?

Performance Optimisation and AdministrationMedium
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EVALUATE SUMMARIZECOLUMNS( 'Date'[Fiscal Year], 'Product'[Category], "Sales", [Total Sales], "Margin", [Margin %] ) ORDER BY 'Date'[Fiscal Year] Turn on Server Timings and Clear cache before running to see storage engine and formula engine time. The same EVALUATE syntax works in the DAX query view in Desktop.

Frequently asked questions

What does a Power BI / BI Architect do?

BI Architects design the overall analytics platform: shared semantic models, workspace and capacity strategy, security, deployment pipelines, Git-based development and Fabric components like lakehouses and Direct Lake. They set standards for modelling, naming and performance, guide developer teams and work with data engineering and security teams. Interviews test architecture judgement, governance and large-scale performance tuning experience. Strong communication with leadership teams is also essential.

Which skills are tested in a Power BI / BI Architect interview?

Expect questions on Fabric architecture, Capacity planning, Governance and security, Performance tuning, CI/CD for BI. Most rounds also ask you to explain a project and solve one practical problem live.

How do I prepare for a Power BI / BI Architect interview?

Revise Performance Optimisation and Administration, Power BI Service, Sharing and Security, Data Modelling, Advanced DAX and Time Intelligence first using the topic sheets, practise the questions on this page aloud, then do one full mock interview to practise timing.

Topic sheets for this role

Performance Optimisation and Administration questionsPower BI Service, Sharing and Security questionsData Modelling questionsAdvanced DAX and Time Intelligence questions

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