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Top 25 Interview Questions Answers - Denodo Developer

Written by Pratibha Sinha | Nov 11, 2025 4:50:13 AM


1. What is Denodo?

Denodo is a data virtualization platform that allows organizations to integrate, manage, and deliver data in real-time without physically moving or replicating it. It provides a unified data view across multiple sources such as databases, cloud systems, big data platforms, and APIs.

2. What is Data Virtualization?

Data virtualization is a logical data integration technique that lets users access and query data from multiple systems as if it resides in one place, without copying or transferring it. It improves agility and reduces data latency.

3. What are the key features of Denodo?

  • Real-time Data Access
  • Unified Data Layer
  • Query Optimization & Performance Tuning
  • Caching Mechanism
  • Data Governance & Security
  • Metadata Management
  • Connectivity with Cloud, BI tools & APIs

4. How is Denodo different from ETL tools?

Denodo (Virtualization) ETL Tools (Extraction & Loading)
Does not move data Moves and stores data
Real-time data access Batch data access
Faster implementation Time-consuming
Minimal storage needs Requires additional storage


5. What is a Virtual Database (VDB) in Denodo?

A Virtual Database is a logical database created in Denodo to organize views, configure roles, and maintain security policies. It acts as a workspace for data modeling and virtualization.


6. What types of views exist in Denodo?

  • Base View: Direct representation of a data source
  • Derived View: Created by transforming/combining base views
  • Parameterized View: Accepts runtime input parameters
  • Interface View: Used for data service exposure, like REST/SOAP

7. What is Denodo VDP?

VDP (Virtual DataPort) is the core engine of Denodo that handles:

  • Query execution
  • Data source connection
  • Security & access control
  • Optimization & caching

8. What is the Denodo Data Catalog?

It is a metadata, search, and annotation tool that allows users to discover, understand, and tag datasets for self-service analytics.

9. What is Caching in Denodo and why is it used?

Caching stores query results temporarily so frequently accessed data can be retrieved faster. It improves performance and reduces load on source systems.

10. Difference between Partial Cache and Full Cache?

Partial Cache Full Cache
Caches only query results Caches complete view data
Used for dynamic sources Used for relatively static data
Less resource consumption More storage needed


11. What are Denodo Data Sources?

  • JDBC / RDBMS Databases
  • Cloud & Big Data platforms (Snowflake, Redshift, Hadoop)
  • Flat Files (CSV, Excel)
  • Web Services (REST/SOAP)
  • OData & GraphQL endpoints

12. Explain Denodo Optimization Techniques.

  • Query Pushdown
  • Caching
  • Data Source Statistics Collection
  • Cost-based Query Optimization
  • Using Aggregation/Pagination in source queries

13. What is Query Pushdown in Denodo?

Query pushdown means Denodo delegates query execution to the source system whenever possible to reduce processing at the virtualization layer and improve performance.

14. What is Denodo Scheduler?

Denodo Scheduler is used for automation tasks like:

  • Cache population
  • Export/import jobs
  • ETL-like scheduled workflows

15. What is a Wrapper in Denodo?

A Wrapper in Denodo is a component that connects Denodo to external data sources and translates Denodo’s logical queries into the source system’s native query language. It ensures seamless communication between Denodo and systems like databases, APIs, or files. Wrappers handle protocol, query syntax, and execution differences automatically. In simple terms, they act as query translators between Denodo and the underlying data sources.

16. How do you secure data in Denodo?

  • Role-based access control
  • Row-level & column-level restrictions
  • Data masking
  • SSL/TLS encryption
  • OAuth / SAML integration

17. What is Data Masking in Denodo?

Data Masking in Denodo is the process of hiding or obfuscating sensitive data such as personal or financial information. It allows developers and analysts to work with realistic datasets without exposing confidential details. This is achieved using masking functions like substring, encryption, nulling, or randomization.

18. How to handle incremental data refresh in Denodo Cache?

Incremental cache refresh in Denodo is handled by configuring Custom Cache Invalidation Policies that refresh only the updated records instead of the full dataset. This is often achieved using timestamp or primary key-based filters in cache queries. The Denodo Scheduler is used to automate these incremental cache refresh jobs.

19. What is Denodo REST Web Service?

Denodo REST Web Service allows you to expose Denodo views as RESTful APIs so external applications can access virtualized data in real-time. It supports JSON and XML formats for flexible data consumption. This helps integrate Denodo data easily with web apps, BI tools, and third-party systems.

20. What are Interface Views?

Interface Views in Denodo are final output views designed for consumption by end-users, BI tools, or APIs. They act as a clean, standardized layer that hides internal data complexity and transformations.These views help maintain governance, consistency, and simplified data access across systems.

21. Explain Base View Creation Process.

  1. Connect Data Source
  2. Import Metadata
  3. Create Base View
  4. Validate & Query

22. How do you debug slow queries in Denodo?

  • Use Query Monitor
  • Check Execution Trace
  • Analyze Query Plan
  • Optimize joins and conditions
  • Consider caching or pushdown

23. What is Denodo Aggregation Awareness?

Denodo Aggregation Awareness is a feature that allows Denodo to automatically choose the most optimized aggregated dataset when executing queries. It helps improve performance by using pre-aggregated or summary views instead of detailed data when appropriate. This reduces processing time and speeds up reporting and analytics workloads.

24. What are Custom Functions in Denodo?

Custom Functions in Denodo are user-defined Java functions that extend Denodo’s built-in transformation capabilities. They are created when default functions do not meet specific business logic or calculation needs. Once deployed, they can be used directly in views just like standard Denodo functions.

25. Difference between Denodo Platform Control Center vs. VDP Admin Tool.

Denodo Control Center VDP Admin Tool
Starts/stops Denodo services Used for development/configuration
System-level operations View & query management
User and cluster admin Data modeling & access control