What is BigQuery, and how does it differ fundamentally from a traditional relational database or data warehouse?
Junior
Explain the key advantages of using BigQuery for analytical workloads.
Junior
Is BigQuery a database or a data warehouse?
Junior
Why is BigQuery a poor choice for OLTP or high-frequency transactional workloads?
Junior
Is BigQuery a true serverless architecture? Elaborate on what that means for users.
Mid
When would you use BigQuery versus Bigtable, Spanner, or Cloud SQL?
Mid
What are the differences between BigQuery and traditional ETL tools?
Mid
Why might BigQuery be more expensive than Redshift?
Mid
Can Athena replace BigQuery, and what are the use cases for each?
Mid
When choosing between a managed cloud OLAP service like BigQuery and a self-managed columnar cluster, how do they compare across performance predictability, TCO, administrative overhead, query concurrency, and vendor lock-in, and which would you recommend for a team with 20 analysts and occasional heavy ad-hoc queries?
Senior
Which scales better, BigQuery or Redshift, and why?
Senior
Storage Objects & Data Modeling
What are datasets, tables, and views in BigQuery, and when would you use each?
Junior
What are ARRAY and STRUCT data types in BigQuery?
Junior
What is the difference between a table and a view in BigQuery?
Junior
What are native tables, external tables, and BigLake tables in BigQuery, and what are their primary use cases?
Mid
Explain the UNNEST operator in BigQuery and how it is used to flatten ARRAYs or STRUCTs.
Mid
How does BigQuery handle primary and foreign keys, and what are the implications compared to a traditional RDBMS that enforces these constraints?
Mid
Does BigQuery support all regions, and why is dataset location important?
Mid
How do you model nested and repeated data, and when do you UNNEST vs normalize into separate tables?
Senior
Explain ARRAYs and STRUCTs in BigQuery. Why is denormalizing data into nested and repeated fields often considered idiomatic and performant?
Senior
What are the best practices for schema design in BigQuery for analytical workloads?
Senior
What does the term lakehouse mean for BigQuery, and how do BigLake tables move it in that direction?
Senior
Data Types & Schema
What data types does BigQuery support?
Junior
What are the key data types supported by BigQuery, and how might choosing the right data type impact storage, performance, and cost?
Junior
How does schema auto-detection work when loading data into BigQuery, and when should you provide an explicit schema instead?
Junior
How does BigQuery support schema evolution, and what types of schema changes are allowed without data loss?
Mid
When would you use NUMERIC versus BIGNUMERIC versus FLOAT64 in BigQuery, and why does precision matter for financial data?
Mid
How does the native JSON data type in BigQuery differ from storing JSON as a string, and what are the advantages?
Mid
Architecture & Query Execution
When data is loaded into BigQuery, where is it physically stored?
Junior
Can I see or access the actual files behind a BigQuery table?
Junior
What format does BigQuery store data in internally?
Junior
Can you explain the high-level architecture of BigQuery?
Mid
What are BigQuery slots, and how do they represent the unit of computational capacity?
Mid
What happens to the data if a BigQuery node fails?
Mid
Describe the high-level architecture of BigQuery, specifically how it separates storage and compute. Why is this separation beneficial?
Senior
Explain the roles of Dremel, Colossus, and Jupiter in BigQuery's architecture and query execution.
Senior
Explain what a columnar database is and how BigQuery leverages columnar storage (Capacitor format) for analytical performance.
Senior
When you submit a SQL query in BigQuery, how does it physically execute end-to-end, and what factors affect its speed?
Senior
What is the persistence layer in BigQuery (Colossus), and how does it ensure durability?
Senior
Explain BigQuery's architecture, including columnar storage and slot-based compute, and how it fundamentally differs from traditional databases.
Senior
What is the in-memory shuffle tier in BigQuery, and what role does it play during query execution?
Senior
Can you describe Dremel's tree architecture — the roles of the root, mixer, and leaf nodes — during a query?
Senior
How are slots scheduled and shared among concurrent queries and users in BigQuery?
Senior
What is the difference between a broadcast join and a hash join in BigQuery, and how does the engine decide?
Senior
What transaction and consistency guarantees does BigQuery provide, including multi-statement transactions and the streaming buffer?
Senior
Partitioning & Clustering
What is partitioning in BigQuery, and how does it help performance?
Junior
Describe how partitioning and clustering work in BigQuery and how they contribute to optimizing query performance and cost.
Mid
What is clustering in BigQuery, and how does it differ from partitioning?
Mid
What is the difference between ingestion-time partitioning and column-based partitioning?
Mid
Explain partitioning in BigQuery. What are the different types of partitioning available, and when would you choose one over another?
Mid
When should you use partitioning vs clustering, and how do they impact cost and performance?
Mid
How does partition pruning work, and what are the requirements for a query to effectively leverage it?
Mid
How would you apply partitioning on a table that only has string columns like id, name, and address?
Mid
Explain the concept of clustering in BigQuery and its benefits for query performance.
Mid
What is require_partition_filter, and why would you enable it on a table?
Mid
What considerations should be taken into account when changing a partitioning column on an existing BigQuery table?
Senior
What is the partition limit in BigQuery, and what problems arise when partitions are too small or too numerous?
Senior
What is automatic reclustering in BigQuery, and how does it keep clustered tables performant over time?
Senior
Data Loading Ingestion & Export
Describe the common methods for batch loading data into BigQuery from Google Cloud Storage.
Junior
How do you export data out of BigQuery, and what are the differences between EXPORT DATA statements and extract jobs?
Junior
Explain the concept of BigQuery federated queries and when you would use them versus loading data.
Mid
Why is Google Cloud Storage often used as an intermediary storage layer when loading data into BigQuery?
Mid
What are the common ways to load data into BigQuery, and when would you pick each?
Mid
What is the BigQuery Data Transfer Service, and how does it simplify data ingestion?
Mid
How would you handle late-arriving or duplicated data when performing streaming inserts into BigQuery?
Senior
Explain the different options for streaming data into BigQuery (legacy streaming insert API vs. Storage Write API) and their characteristics regarding quotas, cost, and deduplication.
Senior
Why is it recommended to use the Storage Read API for reads and the Storage Write API for writes for best performance in BigQuery?
Senior
Cost Model & Optimization
Can you explain BigQuery's cost model?
Junior
Why is SELECT * considered a bad practice in BigQuery, especially considering its columnar storage and pricing model?
Junior
How do you estimate the cost of a BigQuery query before running it?
Junior
Does the LIMIT clause reduce query cost in BigQuery?
Junior
How does table and partition expiration work in BigQuery, and why would you configure it?
Junior
Explain the difference between BigQuery's on-demand pricing and capacity-based (slot) pricing models. When would an organization choose one over the other?
Mid
How can you optimize data storage costs in BigQuery?
Mid
What is query caching in BigQuery, and under what conditions does it apply or not apply?
Mid
How can you reduce bytes processed in BigQuery to optimize costs?
Mid
What is the difference between active storage and long-term storage pricing, and how does a table qualify for long-term storage?
Mid
How would you put guardrails on a runaway BigQuery bill using maximum_bytes_billed and custom quotas?
Mid
What are approximate aggregate functions like APPROX_COUNT_DISTINCT, and when would you trade exactness for cost and speed?
Mid
Explain BigQuery's pricing model, including on-demand versus flat-rate, and discuss strategies to control spiraling costs.
Senior
What is the difference between logical and physical storage billing in BigQuery, and how do you decide which to use?
Senior
Sql Features & Dml
What is the difference between Standard SQL and Legacy SQL in BigQuery?
Junior
What are the various ways to access BigQuery once configured?
Junior
Explain the concept of window functions in BigQuery and how they differ from aggregate functions.
Mid
Describe the different types of User-Defined Functions available in BigQuery (SQL, JavaScript, Remote Functions) and when you would use each.
Mid
What are wildcard tables in BigQuery, and when are they useful?
Mid
Should you use TRUNCATE TABLE or DELETE to remove all rows in BigQuery, and what are the implications of each?
Mid
What does the QUALIFY clause do in GoogleSQL, and why is it useful?
Mid
What are stored procedures and scripting in BigQuery, and when would you reach for them?
Mid
Why can CROSS JOINs be dangerous in BigQuery, and how do you avoid accidental ones?
Mid
What are the INFORMATION_SCHEMA views in BigQuery, and what kinds of metadata and operational questions can you answer with them?
Mid
How does the MERGE statement work in BigQuery, and how would you use it to implement upserts or slowly changing dimensions?
Senior
What are the cost and quota characteristics of DML operations (UPDATE/DELETE/MERGE) in BigQuery, and how do they differ from a traditional RDBMS?
Senior
Views & Materialization
What is the difference between a standard view and a materialized view in BigQuery, and when would you use each?
Mid
Can you explain the concept of materialized views in BigQuery?
Mid
What is the difference between temporary, permanent, and materialized views in BigQuery?
Mid
What are table functions (TVFs) in BigQuery, and how do they differ from views and scalar UDFs?
Mid
When do you use materialized views vs scheduled queries vs persisted tables for dashboards?
Senior
Query Performance Tuning
What are the best practices for optimizing query performance and cost in BigQuery?
Mid
Why is the ORDER BY clause expensive in BigQuery?
Mid
What are query stages in a BigQuery execution plan, and how do you read them to understand what the engine did?
Mid
How would you design a BigQuery table for a large volume of daily event logs (e.g., 5 TB), considering performance and cost?
Senior
How do you analyze a BigQuery query execution plan to identify performance bottlenecks and optimize query performance?
Senior
Describe strategies to handle data skew in BigQuery queries during joins or aggregations.
Senior
What happens if you increase SQL query concurrency in BigQuery?
Senior
How would you optimize a slow dashboard query running on billions of rows in BigQuery?
Senior
Security Governance & Compliance
How does access control work in BigQuery, including IAM roles and granular features like row-level and column-level security?
Mid
Explain authorized views and authorized datasets as mechanisms for sharing data securely in BigQuery.
Mid
What is the BigQuery Data Catalog, and how does it contribute to data governance?
Mid
How does BigQuery ensure data encryption at rest and in transit?
Mid
What is the difference between the jobUser and dataViewer roles in BigQuery, and why is that distinction important?
Mid
What is the best approach to guarantee GDPR compliance when storing data in BigQuery?
Senior
What are policy tags and dynamic data masking in BigQuery, and how do they enforce column-level governance?
Senior
What is CMEK in the context of BigQuery, and when would you use customer-managed encryption keys instead of Google-managed keys?
Senior
What do VPC Service Controls protect against for BigQuery, and why would an organization set them up?
Senior
Orchestration Monitoring & Operations
How can you schedule and automate jobs in BigQuery?
Mid
How do you analyze BigQuery audit logs and INFORMATION_SCHEMA.JOBS for usage analysis and chargeback?
Senior
How do you track pipeline performance, debug issues, and optimize query costs in BigQuery?
Senior
How do you orchestrate BigQuery pipeline workflows using tools like Cloud Composer, Cloud Functions, or Cloud Scheduler?
Senior
Capacity Recovery & Data Sharing
Explain the concept of BigQuery's time travel feature and how it can be used for data recovery.
Mid
What is BigQuery BI Engine, and how does it accelerate dashboard and reporting performance?
Mid
Explain the difference between BigQuery slots and slot reservations.
Mid
What is the difference between a table snapshot and a table clone in BigQuery, and when would you use each?
Mid
What is the difference between time travel and the fail-safe period in BigQuery?
Mid
What is Analytics Hub, and how does it enable data sharing and data exchanges across organizations in BigQuery?
Mid
Why does a cross-region join fail in BigQuery, and how do you move data between regions to work around it?
Mid
What are BigQuery Editions (Standard, Enterprise, Enterprise Plus), and how does slot autoscaling work within them?
Senior
What is the difference between slot commitments and autoscaling reservations, and how are idle slots shared across reservations?
Senior
What is BigQuery Omni, and what problem does it solve for multi-cloud analytics?
Senior
Machine Learning & Ai
What is BigQuery ML, and what types of machine learning models can you train and deploy directly within BigQuery using SQL?
Mid
What do ML.PREDICT, ML.EVALUATE, and ML.FORECAST do in BigQuery ML, and how do they fit the model lifecycle?
Mid
When would you choose to train a model using BigQuery ML versus exporting data to a service like Vertex AI?
Senior
What is the TRANSFORM clause in BigQuery ML, and why is it valuable for preprocessing?
Senior
What generative-AI and vector-search capabilities does BigQuery offer, and what use cases do they enable?
Senior
Top 134 BigQuery Interview Questions And Answers 2025 | TechPrep