ETL Developer interview questions & mock practice
What interview questions are asked for an ETL Developer?
An ETL Developer interview in 2026 runs across 4 rounds — sql & data warehousing, etl tool round, pipeline / scenario, behavioural. Below are the most-asked ETL Developer interview questions and a focused prep plan. Rehearse every answer out loud with the free timed practice below before the real one.
- SQL
- Data Warehousing
- Informatica
- SSIS
- Dimensional Modelling
- Data Pipelines
- Performance Tuning
- Unix Shell Scripting
Free interview practice · ETL Developer
Practise your ETL Developer interview now — free
Step through the 14 most-asked ETL Developer questions one at a time, under a timer, just like the real thing. Jot your answer, then reveal what a strong answer covers. No signup needed to practise.
The ETL Developer interview process
Data pipelines, transformations and warehouse loading for the ETL role across banking, IT services and data-engineering teams in India.
1. SQL & data warehousing
Complex queries, joins, and dimensional modelling concepts.
2. ETL tool round
Informatica, SSIS, Talend or DataStage mappings and transformations.
3. Pipeline / scenario
Designing an incremental load, SCD handling and error recovery.
4. Behavioural
Handling production failures, deadlines and cross-team coordination.
Most-asked ETL Developer interview questions
14 of the questions ETL Developer candidates are asked most often in India. Practise answering each one out loud in the timed practice above.
- 1. What is the difference between ETL and ELT and when would you use each?
- 2. Explain the difference between a fact table and a dimension table.
- 3. What is a Slowly Changing Dimension and explain Type 1, Type 2 and Type 3?
- 4. What is the difference between a star schema and a snowflake schema?
- 5. How do you perform incremental loading instead of a full load?
- 6. What is the difference between a connected and an unconnected lookup in Informatica?
- 7. Explain the difference between a router and a filter transformation.
- 8. What is a surrogate key and why is it used in a data warehouse?
- 9. How do you handle duplicate records in an ETL pipeline?
- 10. What is the difference between a static and a dynamic cache in a lookup?
- 11. How do you handle errors and rejected rows in an ETL job?
- 12. What strategies do you use to tune the performance of a slow-running ETL job?
- 13. Explain the difference between truncate-and-load and upsert (merge) loading.
- 14. Describe a time a nightly load failed in production and how you recovered.
How to prepare for your ETL Developer interview
Be fluent in dimensional modelling: facts, dimensions, surrogate keys and all SCD types with concrete examples.
Know your primary ETL tool deeply (Informatica, SSIS or Talend) including transformations, mappings and parameterisation.
Practise writing complex SQL: joins, window functions, deduplication and set operations for transformations.
Prepare incremental-load and change-data-capture scenarios, plus error handling and restartability of jobs.
Review performance tuning: partitioning, pushdown optimisation, indexing and bulk-load options.
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Interview prep guides
ETL Developer interview — FAQs
What questions are asked in an ETL Developer interview?
Common ETL Developer interview questions include: What is the difference between ETL and ELT and when would you use each? Explain the difference between a fact table and a dimension table. What is a Slowly Changing Dimension and explain Type 1, Type 2 and Type 3? What is the difference between a star schema and a snowflake schema? Interviews usually run across 4 rounds — SQL & data warehousing, ETL tool round, Pipeline / scenario, Behavioural. Practise them with the free timed practice on this page.
How many rounds are in an ETL Developer interview?
A typical ETL Developer interview has 4 rounds: SQL & data warehousing (Complex queries, joins, and dimensional modelling concepts.); ETL tool round (Informatica, SSIS, Talend or DataStage mappings and transformations.); Pipeline / scenario (Designing an incremental load, SCD handling and error recovery.); Behavioural (Handling production failures, deadlines and cross-team coordination.).
How do I prepare for an ETL Developer interview?
To prepare for an ETL Developer interview: Be fluent in dimensional modelling: facts, dimensions, surrogate keys and all SCD types with concrete examples. Know your primary ETL tool deeply (Informatica, SSIS or Talend) including transformations, mappings and parameterisation. Practise writing complex SQL: joins, window functions, deduplication and set operations for transformations. Then rehearse every question out loud with the timed practice on this page before the real thing.
What skills do I need for an ETL Developer role?
Core ETL Developer skills tested in interviews include SQL, Data Warehousing, Informatica, SSIS, Dimensional Modelling, Data Pipelines, Performance Tuning, Unix Shell Scripting. OnJob shows you exactly which of these skills stand between you and a 100% match on every live ETL Developer job.
Is the ETL Developer mock interview practice free?
Yes. The questions, the answer guidance and the timed practice on this page are free and need no signup. With a free OnJob account you can also take timed role tests and free certification tests. Personalised AI role and skill tests are part of the paid plans.
Ace your ETL Developer interview
Rehearse every ETL Developer question out loud on this page, then sign in to take a timed role test or a free certification in the OnJob practice hub.