Vipen Koul, Performance Tuning Developer in Bothell, WA, United States
Vipen Koul

Performance Tuning Developer in Bothell, WA, United States

Member since May 24, 2019
Vipen is a highly experienced database warehouse, development, and performance professional with comprehensive knowledge of OLAP and OLTP databases. He has worked as a data architect, data modeler, ETL developer, database developer, and data analyzer utilizing Vertica, Teradata, Netezza, Oracle, and SQL Server, as well as Snowflake and Python.
Vipen is now available for hire




Bothell, WA, United States



Preferred Environment

Multi-dimensional Databases, Git, Subversion (SVN), Windows, Linux

The most amazing...

...things I've done was design various management systems and resolve performance issues involving various database technologies.


  • Senior DBA

    2010 - PRESENT
    • Supported database environments, backups/recovery, access management, and reporting, ensuring user access compliance with company policies. User security model as per company policy of least privilege together with the needs of the clients.
    • Managed performance tuning, and upgrades of MPP and cloud DBs. Led full-scale testing of newer upgrades and roll out after deep analysis on performance/features/user connectivity and user acceptance.
    • Developed tools to augment testing and equipping the offshore team for providing effective off-hours support for clients and loads. Mentored junior members of the team to equip them to handle critical situations with a fair amount of ease.
    • Designed data collection and management reporting systems around database usage and ETL SLAs, forming a basis for cost center billing of respective departments. Designed and developed ETLs in Informatica and other tools.
    • Handled clickstream data, data lakes, developed processes to efficiently transfer terabytes of data between old and new databases during the cross-database migration.
    • Analyzed query plans across various database technologies and provided solutions with efficient SQL. Very hands-on SQL and performance tuning. Augmented the DB system with additional performance metrics of queries for tuning of various DB parameters.
    • Wrote complex SQL for handling large data extraction, large dataset analysis, and large data uploading. Handled hierarchical data and output flat datasets and vice versa.
    • Performed data analysis, dimensional data modeling for large data set objects with terabytes of data. Logical and physical design separation geared towards performance and ease of development. Common data model design to have a unified view of data.
    • Worked on data mapping between different data sources for matching, lineage, and consistency. Maintained data marts for reporting and support for data feeding to downward systems. Built lineage logic between distributed data sets from various feeds.
    • Snowflake database and user management. Building Snowflake data pipelines and maintaining slowly changing dimensions. Dimensional modeling in Snowflake.
    Technologies: Oracle, Teradata, Snowflake, Netezza, Vertica
  • Freelancer

    2010 - 2014
    • Contributed to bug fixing and enhancements on the database side to support user functions in the web application.
    • Created the web application while keeping in mind the retail industry functions and requirements. The application is currently being used by jewelry vendors.
    • Designed the UI so it can be built on any stack and connected to any DB technology which supports stored procedures in DB or at the application tier level.
    • Reduced page response times to less than three seconds and ensured growth would not negatively impact response times.
    Technologies: .NET, Microsoft SQL Server, PHP, MySQL
  • Freelancer

    2010 - 2013
    • Refactored a clinical auditing data system in regards to data structures for making it very easy for the UI to show what changed at the column level.
    • Replaced the older partitioning scheme with a new composite equipartitioning scheme for faster retrieval of records on a data set with TBs of data.
    • Complex SQL for handling large XML dataset for analysis and uploading with native database technologies.
    • Wrote performant queries/programs to analyze hierarchical data for trail on auditing data.
    • Performed migration and switch from older clinical trial systems data to new systems. Gathered requirements for the work assessment.
    • Worked on creating data mapping scripts for successful initial data transfer as per the new system requirement from older systems. The process was designed to ease the migration from any system.
    Technologies: Toad, Oracle
  • Lead Software Engineer

    2005 - 2009
    Sumtotal Systems
    • Led application/database/SQL performance tuning. Put major effort in modifying ASPEN tool written in XSLT language to generate a performance-oriented SQL signature for Oracle & SQL Server. It was incorporated and used for future product development. First, the need was the best performing SQL for pagination queries which would generate the best response time and then worked backward to rewrite tools to generate it flawlessly. Product after a good size data was not performing and clients were not happy.
    • Periodically reviewed SQL/Process for refactoring. Made application better with less code running and implementing new DB features. One piece of PL/SQL process which had one core pegged to 100% all the time due to recursion was replaced by simple construct of CONNECT BY PRIOR clause to do the same task.
    • Tested new releases and incorporating new enhancements in the product. Member of engineering group responsible for product's new direction and road map. Provided many useful fixes for the overall health of the product in our data center servers.
    • Resolved performance issues around webservers, DB servers, and applications with live client sessions. Identified the new hot areas for potential problems. Involved in many pre-sales stress testing for clients to show them confidence in our product. The use cases were being provided by the client. Involved in in-house concurrent user stress tests from 1000 to 5000 and gathering trace data for subsequent analysis and looking for the areas to improve the throughput of the application on a given hardware. Earned Power-Of-One and other awards during my employment.
    • Wrote SOP for best practices around the LMS application usage, how to troubleshoot, what to gather, what to look for and how to document it for routing it to sustained engineering. Provided expert guidance and fixes for the data synchronization tool to run under a couple of hours instead of days.
    • Designed queries for handling hierarchical data and output flat datasets and vice versa.
    Technologies: Microsoft SQL Server, Oracle
  • Consultant

    2005 - 2005
    • Developed software solutions for power companies using Oracle advanced queues. Worked on modules to determine the optimal power throughput through the transmission lines.
    • Led Oracle SQL and PL/SQL performance tuning. Optimized packages and procedures.
    • Used the Oracle queues to implement a data pipeline with fault tolerance.
    Technologies: Oracle
  • Lead Software Engineer

    2003 - 2005
    State of Washington
    • Involved in requirements gathering for the reporting needs. Performed initial data analysis and gauging the work needed to provide the reporting solution. Setup data structures and cleanup needed for the reporting data collection.
    • Modeled reporting database Designed management reports. Architect the Data warehouse for the management reporting database. Data collection and reports optimal execution.
    • Triaged the reporting issues around missing data, data volume changes, and performance.
    • Managed performance tuning issues arising out of the reports from time to time with database and after upgrading, user change requirements, augmenting existing reports with additional data sets for management.
    Technologies: Toad, Oracle
  • DBA

    2001 - 2003
    Aventis Pharmaceutical
    • Handled day-to-day Oracle database administration. Monitored the database and made sure the database was working optimally. Worked on Performance tuning of the database, application and queries.
    • Designed user access security system for the web-based application for medical publications. The security system was very easy to follow and it had a tiered level of privileges.
    • Analyzed data structures, provided code reviews, and tested SQL, PL/SQL in pre-production environment for sizeable data to have a better confidence in moving the deployment to production.
    • Implemented an Oracle database replication. The replication was simple master-to-offsite replication.
    Technologies: ASP, Oracle
  • Contractor

    1999 - 2001
    • Supported the credit analysis of product development for companies. Developed complex Oracle PL/SQL procedure for doing Financial-what-if analysis for determining credit score and limit for companies. Created processes for financial models.
    • Worked with customers for a successful transition from old systems with data transfers and complex data migration.
    • Oversaw SQL performance tuning for the data transfer interfaces written for loading data from operational systems to application tables for analysis. Provided solutions for performance issues arising out of the product for customers.
    • Worked on data mapping between different data sources for matching, lineage, and consistency. Worked on the migration of data from older applications and flat files for successful customer adoption of the new product.
    Technologies: Microsoft SQL Server, Oracle


  • Netezza to Vertica Migration (Development)

    1. Assessing the code changes and challenges to be in the migration path and how to resolve them.
    2. Assessing the new workload on the existing systems for the data transfer routines and database resource allocation.
    3. Keeping the existing system in working order even under the increased load.

  • Tuning Nightly Loads (Development)

    1. Nightly loads to finish well before 4 AM so that even in the event of any set of failures, loads would finish well before the 6 AM SLA.
    2. Capture all expensive SQLs from query history and tuned the most expensive ones.
    3. Provided feedback to developers for effective coding principles and data layout

  • Enhancing Starlims Application (Development)

    1. The data was spread into un-even Oracle table partitions.
    2. It was difficult for UI to perform by flattening the XML data and then find the information change.
    3. I replaced the original table partitioning with new enhanced composite partitioning with inventing equipartitioning formula for the average number of rows inside each partition.
    4. Flatten the XML data and carved out the changes in columns between the two adjacent record's XML data, stored it into UI tables for easy reporting.

  • Purchase/Materials/Financial Management System (Development)

    1. Designed the system for the client with multiple implementations at various branches.
    2. Trained the staff on the usage of the system.
    3. The low-level design was engineered by keeping all potential performance issues that could arise with large data accumulation.
    4. Designed the reporting for upper management.
    5. User and system documentation.

  • Financial What-If Analysis for Credit Check for Companies (Development)

    1. The user used to work on many screens to generate a report for what-if analysis for credit analysis.
    2. Designed and coded the whole process in Oracle and after its run, it would accumulate data in oracle tables for the final numbers of what-if-analysis.

  • Snowflake (Development)

    Supporting snowflake production and development environments
    Maintaining data pipelines
    Providing user access and privileges to the database objects
    Dimensional modeling & maintaining the ETL pipelines.

  • Clickstream (Development)

    Ingestion of Clickstream data on a near real-time basis
    Ingested data is converted into facts and dimensions (some are slowly changing)
    Data is made available to clients and downstream data marts
    Maintaining data loading SLAs
    Resolving data conflicts and operational issues.


  • Languages

    Stored Procedure, Transact-SQL, SQL, T-SQL, Python, Snowflake, C, PHP
  • Tools

    Cron, Toad, Spotfire, AWS Athena, Microsoft Access, AWS Glue, MySQL Performance Tuning, Teradata SQL Assistant, Informatica ETL, DbVisualizer, Erwin, Turbo Pascal, Subversion (SVN), Git, BigQuery
  • Paradigms

    ETL, Database Design, Dimensional Modeling, Refactoring, Acceptance Test-driven Development (ATDD), Test-driven Development (TDD)
  • Storage

    Oracle DBMS, Database Architecture, Database Migration, DB, Database Modeling, Databases, SQL Stored Procedures, Relational Databases, Database Transactions, Database Triggers, Data Pipelines, Oracle SQL, Oracle 12c, PL/SQL, Oracle RDBMS, Database Administration, SQL Performance, Database Performance, Vertica, Netezza, Oracle PL/SQL, SQL Developer, MySQL, Microsoft SQL Server, PostgreSQL, Database Administration (DBA), SQL Server 2017, Oracle Multitenant, MongoDB, AWS S3, SQL Azure, Teradata, SQL Server DBA, MariaDB, Cassandra, MemSQL, SQL Server Integration Services (SSIS), Redshift, Amazon Aurora, Multi-dimensional Databases
  • Other

    Informatica, Star Schema, Database Optimization, Database Table Optimization, Query Optimization, Data Warehouse Design, Stored Procedures, Stored Procedure Tuning, Stored Procedure Refactoring, Data Architecture, Architecture, ETL Pipelines, PL/SQL Tuning, Performance Tuning, ETL Development, Data Warehousing, Data Modeling, Data Analysis, Complex Data Analysis, Data Engineering, Data Management, Data Marts, Debugging, AWS, Electronic Data Interchange (EDI), Big Data, ETL Tools, Google BigQuery, Data Auditing, Apache Cassandra, Oracle OEM 12c, Microsoft Data Transformation Services (now SSIS), Computer Science, Mathematics
  • Frameworks

    Presto DB, ASP, .NET
  • Platforms

    KornShell, Amazon Web Services (AWS), Linux, Windows, Azure, Oracle, Google Cloud Platform (GCP)
  • Industry Expertise



  • Master of Computer Applications Degree in Computer Science
    1990 - 1993
    Himachal Pradesh University - Shimla, India
  • Master of Science Degree in Mathematics
    1985 - 1987
    University of Jammu - Jammu, India
  • Bachelor of Science Degree in Physics, Chemistry, Mathematics, English
    1983 - 1985
    University of Jammu - Jammu, India

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