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Data Warehouse and Dimensional Modeling Questions

Design and model scalable analytical data systems using dimensional modeling principles and data warehouse architecture patterns. Core concepts include fact and dimension tables, defining and enforcing grain, surrogate keys, degenerate and role playing dimensions, conformed dimensions, and handling slowly changing dimensions including Type One, Type Two, and Type Three. Understand schema choices and trade offs such as star schema versus snowflake schema, normalization versus denormalization, and fact table types including transactional, periodic snapshot, and accumulating snapshot. Apply design decisions to meet query patterns and performance goals by considering partitioning, indexing, compression, columnar storage, and aggregation strategies. Be able to design schemas for different business domains, reason about data integration and consistency, and optimize for common analytical workloads and reporting requirements.

EasyTechnical
95 practiced
Explain 'grain' with respect to choosing between invoice-level and invoice-line-level sales facts. For BI reporting needs that include SKU-level performance and invoice-level commission splits, which grain would you choose and why? What are the consequences for storage and ETL?
EasyTechnical
87 practiced
What is a junk dimension and when would you create one? Provide an example with payment_method, is_gift, and promo_code_flag originating from transactional data and explain how combining them into a junk dimension affects ETL and query performance.
MediumTechnical
90 practiced
Given a streaming ingestion that sometimes produces duplicate events (same event_id), write an SQL pattern using window functions to deduplicate and load only the earliest event_time per event_id into the fact table. Provide pseudocode or PostgreSQL-flavored SQL.
HardTechnical
135 practiced
Compare dimensional modeling (Kimball-style) versus Data Vault for enterprise data warehousing. Discuss strengths and weaknesses of each approach for auditability, rapid ingest of changing sources, BI friendliness, and long-term maintenance. When would you recommend a hybrid approach?
MediumTechnical
98 practiced
Describe partitioning strategies for large fact tables (range/date partitioning, hash partitioning, list partitioning). Give an example scenario for each strategy and describe how partition pruning improves query performance for BI queries.

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