Searching for Deloitte ETL testing interview questions, PwC, EY GDS or KPMG? The Big 4 hire ETL and data testers in India for client projects in banking, insurance, healthcare and retail. Their interviews lean towards client scenarios, communication and domain thinking, not just SQL syntax.
What ETL Testers Do at Big 4 Firms
- Test data migrations and warehouse builds for clients, often in finance and regulated industries.
- Validate reports and dashboards that clients use for decisions and compliance.
- Write clear evidence and status updates for client stakeholders.
Typical Interview Rounds
| Round | Commonly reported focus |
|---|---|
| Online test or screening (some roles) | SQL, testing basics, aptitude |
| Technical 1 | SQL queries, ETL and data warehouse concepts, test case design |
| Technical 2 / client-style scenario | Debugging mismatches, domain scenarios, automation exposure |
| Managerial | Estimation, unclear requirements, conflict, prioritisation |
| HR | Motivation, notice period, location |
10 Big 4 ETL Testing Interview Questions With Answers
Q1. Walk me through how you test a data warehouse load end to end.
Requirement and mapping review, test plan, data profiling of source, count and completeness checks, transformation rule checks, data quality (nulls, duplicates, ranges), referential integrity, incremental load checks, report-level validation and sign-off with evidence.
Q2. How do you validate a source-to-target mapping with 200 columns?
Group columns by rule type (direct move, lookup, derived, default). Automate direct-move columns with a MINUS/EXCEPT or hash comparison, write targeted SQL for derived columns, and sample-check lookups. Prioritise columns used in reports and regulatory outputs.
Q3. Write a query to find records in source but not in target.
SELECT customer_id FROM src_customer EXCEPT SELECT customer_id FROM dw_dim_customer;
Q4. How do you test SCD Type 2?
Change a tracked attribute in source, run the load, and confirm the old row is end-dated with current flag N, a new row is inserted with current flag Y, and each business key has exactly one current row. See SCD testing.
Q5. Revenue in the report does not match the source system. How do you investigate?
Confirm filters and date range, compare totals at each layer (source, staging, warehouse, report), check currency and rounding rules, late-arriving data, duplicate joins and time zones. Report the layer where the difference first appears.
Q6. How do you test data in a regulated domain such as banking or insurance?
Add checks for regulatory fields (mandatory, valid codes), full reconciliation of financial totals, audit columns, masking of personal data in test environments and documented evidence for every run.
Q7. How do you handle unclear requirements on a client project?
Raise questions early in writing, log assumptions in the test plan, get them confirmed by the business analyst or client, and mark affected test cases as blocked until confirmed.
Q8. How do you estimate testing effort for a new ETL release?
Count tables and mappings, classify by complexity, estimate per mapping (design, data setup, execution, retest), add regression and buffer, and review with the lead. Show the estimate as a range with assumptions.
Q9. Tell us about a critical defect you found.
Use the STAR format: situation, the check that caught it, the impact (rows, money, report), how you proved it with a query, and what process change prevented it again. A practice-project defect is fine if you present it honestly.
Q10. Why consulting, and why this firm?
Link your goal (variety of client domains, faster learning) to the role, mention the domain or practice you applied for, and show you have read the job description.
How to Prepare
- Practise 20 SQL queries until you can write them without help (SQL query questions).
- Prepare two project stories in STAR format (real-time project explanation).
- Read the client domain in the job description (banking, insurance, healthcare).
- Rehearse a 90-second self introduction.
- Practise the tough and managerial questions.
Interviewing with IT services firms too? See service-company ETL interview questions.
Practise Under Interview Conditions
Reading answers is not the same as answering under time pressure. ETL Testing Interview Questions & Answers – Practice Tests gives you 500+ questions with detailed explanations, from fresher to experienced level, including Python and ETL automation questions alongside SQL, data warehouse and scenario-based rounds. Attempt a test, review every explanation, and retake until you are consistently above 80%.
- Timed practice tests that feel like a real screening round
- Python, automation, SQL and scenario questions in one place
- Detailed answers, so each wrong attempt teaches you something
- Lifetime access and Udemy’s refund policy
Prepare for your ETL testing interview: top 50 questions · in-depth answers · for experienced (3–5 years) · for 10 years experience · SQL query questions · scenario-based questions · data warehouse questions · questions for freshers · free mock test · database testing questions · Python ETL testing questions · Informatica questions · SQL questions for freshers · DBMS questions · data validation questions · service-company questions · ETL automation testing questions · Python test questions · tough questions · self introduction · SQL test MCQs
Frequently Asked Questions
What is asked in a Deloitte ETL testing interview?
Candidates commonly report SQL queries, data warehouse concepts, source-to-target validation, scenario questions about mismatched data and a managerial round on estimation and client communication. It varies by team.
Are Big 4 ETL testing interviews hard?
They are scenario-heavy and expect clear communication, but the technical core is the same: SQL, data warehouse concepts and test design.
Do Big 4 firms hire freshers for ETL testing?
Some campus and entry-level programmes include testing roles. Check current openings on each firm’s careers site.
Is this page official?
No. It is an independent guide and is not affiliated with Deloitte, PwC, EY or KPMG.
Asim Noaman Lodhi
Certified Google Partner · QA Consultant · 12+ Years IT
QA consultant specializing in ETL testing and data quality. Trained 913+ students to transition into data testing roles through hands-on, real-world instruction.