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Vipen Koul, Software Developer in Bothell, United States
Vipen Koul

Software Developer in Bothell, United States

Member since June 18, 2020
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.
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Portfolio

  • InQuest
    SQL, Database Administration (DBA), SQL Performance, Performance Tuning...
  • Toptal Clients
    Microsoft SQL Server, Reverse Engineering, Azure...
  • Freelance
    PostgreSQL

Experience

Location

Bothell, United States

Availability

Part-time

Preferred Environment

Multi-dimensional Databases, Git, Windows

The most amazing...

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

Employment

  • DBA Engineer

    2022 - 2023
    InQuest
    • Performed in-depth analysis of query patterns and query rewrite for performance reasons.
    • Conducted in-depth server analysis, load, and tweaks for optimal MySQL functioning.
    • Designed partitioning on large data tables, did index analysis, removed redundant indexes, and provided SQL scripts for automated partitioning and transforming big monolithic tables to partitioned tables, data movement, and index building.
    Technologies: SQL, Database Administration (DBA), SQL Performance, Performance Tuning, MySQL Performance Tuning

  • DB Performance Engineer

    2021 - 2022
    Toptal Clients
    • Analyzed data demographics and handled performance tuning, data re-factorization, data deduping, and space-saving.
    • Conducted what-if analysis of performance and space usage under the assumption of users in the millions.
    • Reduced space usage by 80% across the board on very large tables with a complex and dynamic SQL procedure built for conditional data de-duping.
    Technologies: Microsoft SQL Server, Reverse Engineering, Azure, Database Lifecycle Management (DLM), MySQL Performance Tuning

  • Postgres DB Performance Engineer

    2021 - 2021
    Freelance
    • Performed performance analysis on the application and the Postgres DB. Re-factored the tables, data, and indices. Achieved excellent SQL query performance with sub-second execution.
    • Advised on overall best practices for data storage.
    • Tracked and resolved existing bugs using a ticketing platform.
    • Validated results and performance metrics while the website was in action with full and stressed loads.
    Technologies: PostgreSQL

  • ETL Engineer

    2020 - 2021
    Toptal Clients
    • Migrated ETL across platforms from Oracle Data Integrator to DBT + Snowflake.
    • Developed the test cases for data validation following best practices for DBT and Snowflake. Performance-tuned the new ETL.
    • Tracked and successfully fixed bugs found within the system.
    Technologies: Data Build Tool (dbt), Snowflake, Data Cleansing, Data Migration, Amazon Athena, Oracle Database, Git

  • Senior DBA

    2010 - 2020
    Telecommunication & Content Provider
    • Supported database environments, backups/recovery, access management, and reporting, ensuring user access compliance with company policies.
    • Managed performance tuning and upgrades of MPP and cloud DBs. Led full-scale testing of newer upgrades and roll-out after deep analysis of performance/features/user connectivity and user acceptance.
    • Developed tools to augment testing, equipping the offshore team to provide effective off-hours support for clients and loads. Mentored junior team members to enable 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 and 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 built solutions with efficient, hands-on SQL and performance tuning. Augmented the DB system with additional performance metrics of queries to tune various DB parameters.
    • Wrote complex SQL to handle large data extraction, analysis, and uploading. Handled hierarchical data and output flat datasets and vice versa.
    • Analyzed data and did dimensional data modeling for large objects with terabytes of data. Geared logical and physical design separation toward performance and ease of development. Created a unified data model.
    • 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.
    • Managed the Snowflake database and users, built pipelines and maintained slowly changing dimensions, and handled dimensional modeling.
    Technologies: Oracle, Teradata, Snowflake, Netezza, Vertica, Dimensional Modeling, Azure SQL, Amazon S3 (AWS S3), ETL Pipelines, SQL Performance, ETL Tools, DbVisualizer, Teradata SQL Assistant, Oracle Multitenant, Erwin, Informatica ETL, KornShell, Database Administration (DBA), Debugging, Data Marts, Data Engineering, Oracle RDBMS, Database Modeling, Database Migration, DB, Complex Data Analysis, Data Analysis, ETL Development, Stored Procedure Refactoring, Refactoring, Stored Procedure Tuning, Stored Procedure, Database Table Optimization, Database Optimization, Star Schema, Performance Tuning, PL/SQL Tuning, T-SQL (Transact-SQL), Linux, Oracle OEM 12c, PL/SQL, Data Pipelines, Database Transactions, Relational Databases, SQL Stored Procedures, Databases, Database Architecture, Database Design, ETL, Toad, Oracle PL/SQL, SQL, Informatica, Data Warehousing, Data Warehouse Design, Data Migration, Analytics, Redshift, Pandas, Big Data, Big Data Architecture, Application Architecture, Data Analytics, Python, MySQL Performance Tuning, Microsoft Access, Amazon Athena, Amazon Web Services (AWS), Cassandra, SQL Server Integration Services (SSIS), MemSQL, Database Schema Design, Integration, Database Lifecycle Management (DLM), Oracle Database

  • Freelance Developer

    2010 - 2014
    Retailer
    • 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, SQL Performance, Debugging, DB, Stored Procedure Refactoring, Stored Procedure Tuning, Stored Procedure, Database Optimization, Performance Tuning, Azure, T-SQL (Transact-SQL), SQL Server DBA, Database Transactions, Relational Databases, SQL Stored Procedures, Databases, ETL, SQL, Google Cloud Platform (GCP), Database Schema Design

  • Freelance Developer

    2010 - 2013
    Pharmaceutical Company
    • Refactored a clinical auditing data system in regards to data structures to make 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.
    • Wrote complex SQL for handling a large XML dataset for analysis and uploading with native database technologies.
    • Created performant queries/programs to analyze hierarchical data for a trail on auditing data.
    • Performed migration and switch from older clinical trial systems data to new systems. Gathered requirements for the work assessment.
    • Created 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, Oracle 12c, Oracle RDBMS, Stored Procedure, SQL Performance, Debugging, Database Administration (DBA), DB, Data Analysis, ETL Development, Stored Procedure Refactoring, Stored Procedure Tuning, Database Table Optimization, Database Optimization, Performance Tuning, PL/SQL Tuning, Spotfire, Linux, Oracle OEM 12c, PL/SQL, Database Transactions, Relational Databases, Databases, Database Design, Oracle PL/SQL, SQL, Reverse Engineering, Database Schema Design, Oracle Database

  • Lead Software Engineer

    2005 - 2009
    Sumtotal Systems
    • Led application/database/SQL performance tuning. Put major effort into modifying ASPEN written in XSLT to generate a performance-oriented SQL signature for Oracle and SQL Server. It was incorporated and used for future product development.
    • Periodically reviewed SQL/Process for refactoring. Made the application better with less code running and implemented new DB features—for example, replaced a recursive process with a CONNECT BY PRIOR clause to do the same task.
    • Tested new releases and incorporated new enhancements into the product as a contributing member of the engineering group that owned the product's new direction and roadmap.
    • Provided many useful fixes for the overall health of the product in our data center servers.
    • Resolved performance issues around web servers, DB servers, and applications with live client sessions. Identified the new hot areas for potential problems and contributed to pre-sales stress testing.
    • 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 in under a couple of hours instead of days. Earned power-of-one and other awards during my employment.
    • Designed queries for handling hierarchical data and output flat datasets and vice versa.
    Technologies: Microsoft SQL Server, Oracle, Stored Procedure, SQL Performance, ETL Tools, ASP, Subversion (SVN), Debugging, Data Engineering, Oracle RDBMS, Database Triggers, DB, ETL Development, Stored Procedure Refactoring, Stored Procedure Tuning, Database Table Optimization, Database Optimization, Star Schema, Performance Tuning, PL/SQL Tuning, T-SQL (Transact-SQL), SQL Server DBA, Linux, PL/SQL, Database Transactions, Relational Databases, SQL Stored Procedures, Databases, Database Design, ETL, Toad, Oracle PL/SQL, SQL, Data Migration, Reverse Engineering, Application Architecture, .NET, Database Schema Design, Oracle Database

  • Consultant

    2005 - 2005
    Areva
    • 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, SQL Performance, Debugging, Oracle RDBMS, Database Triggers, DB, Stored Procedure Refactoring, Stored Procedure Tuning, Stored Procedure, Database Optimization, Performance Tuning, PL/SQL Tuning, PL/SQL, Database Transactions, Relational Databases, Databases, Toad, Oracle PL/SQL, SQL, Oracle Database

  • Lead Software Engineer

    2003 - 2005
    State of Washington
    • Gathered requirements for reporting needs. Performed initial data analysis and gauged the work needed to provide the reporting solution. Set up data structures and cleanup needed for the data collection.
    • Modeled a reporting database and designed management reports, architected the data warehouse for the management reporting database, and collected data and optimized reports.
    • 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 post-upgrade features as well as user change requirements. Augmented existing reports with additional datasets for management.
    Technologies: Toad, Oracle, SQL Performance, ETL Tools, Debugging, Data Engineering, Oracle RDBMS, Database Triggers, DB, Data Analysis, ETL Development, Stored Procedure Refactoring, Stored Procedure Tuning, Stored Procedure, Database Optimization, Star Schema, Performance Tuning, PL/SQL Tuning, PL/SQL, Database Transactions, Relational Databases, Databases, Database Design, ETL, Oracle PL/SQL, SQL, Data Warehousing, Data Migration, Analytics, Reverse Engineering, Application Architecture, Database Schema Design, Reporting, Oracle Database

  • DBA

    2001 - 2003
    Sanofi Aventis
    • Handled day-to-day Oracle database administration. Monitored the database and made sure it was working optimally. Performance-tuned the database, application, and queries.
    • Designed a 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 and PL/SQL in a pre-production environment for sizeable data to have better confidence in moving the deployment to production.
    • Implemented an Oracle database replication. The replication was a simple master-to-offsite replication.
    Technologies: ASP, Oracle, SQL Performance, Oracle Multitenant, KornShell, Database Administration (DBA), Debugging, Oracle RDBMS, Database Triggers, DB, Stored Procedure Tuning, Stored Procedure, Database Optimization, Performance Tuning, PL/SQL Tuning, Linux, PL/SQL, Database Transactions, Relational Databases, Databases, Database Design, Toad, Oracle PL/SQL, SQL, Reverse Engineering, .NET, Database Schema Design, Reporting, Database Lifecycle Management (DLM), Oracle Database

  • Contractor

    1999 - 2001
    eCredit.com
    • Supported the credit analysis of product development for companies.
    • Developed a complex Oracle PL/SQL procedure for doing financial what-if analysis for determining credit scores and limits for companies.
    • Created processes for building complex 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.
    • Helped with 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, SQL Performance, Microsoft Data Transformation Services (now SSIS), KornShell, Debugging, Oracle RDBMS, Database Triggers, DB, ETL Development, Stored Procedure Tuning, Stored Procedure, Database Optimization, Performance Tuning, PL/SQL Tuning, SQL Server DBA, PL/SQL, Database Transactions, Relational Databases, T-SQL (Transact-SQL), SQL Stored Procedures, Databases, Toad, Oracle PL/SQL, SQL, C, Integration, Oracle Database

Experience

  • Performance Analysis and Tuning

    What-if analysis on the stress generated and additional resources required if the data grows fourfold as well as the percentage of space-saving on complex data deduping for existing and ongoing data. The analysis was accomplished with an estimated 80% data reduction and minimal indices using a new structure, and I partitioned the SQL Server instance for further performance tuning.

  • Snowflake

    Supported Snowflake production and development environments, maintained data pipelines, provided user access and privileges to the database objects, built dimensional models, maintained the ETL pipelines, and performance-tuned the whole thing.

  • Tuning Nightly Loads

    Nightly loads were set 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. I captured the most expensive SQL queries from the query history and tuned them. After the project was finished, I provided feedback to the developers for effective coding principles and data layout going forward.

  • Clickstream

    Ingestion of Clickstream data on a near real-time basis. The ingested data is converted into facts and dimensions (some are slowly changing). The subsequent data is made available to clients and downstream data marts.

    I maintained data loading SLAs and resolved data conflicts and operational issues.

  • Netezza to Vertica Migration

    Assessed code changes and challenges to the migration path and evaluated how to resolve them. Also looked at the new workload on the existing systems for the data transfer routines and database resource allocation, and kept the existing system in working order even under the increased load.

  • Enhancing Starlims Application

    The data was spread into un-even Oracle table partitions. It was difficult for the UI to perform by flattening the XML data and then find the information change.

    I replaced the original table partitioning with new enhanced composite partitioning by inventing an equipartitioning formula for the average number of rows inside each partition, and I flattened the XML data and carved out the changes in columns between the two adjacent records' XML data, subsequently storing it in UI tables for easy reporting.

  • Purchase/Materials/Financial Management System

    I designed the system for the client with multiple implementations at various branches. The low-level design was engineered by keeping all potential performance issues that could arise with large data accumulation. I designed the reporting for upper management, created all the documentation, and trained the staff in its use.

  • Financial What-if Analysis for Credit Check for Companies

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

Skills

  • Languages

    Stored Procedure, SQL, T-SQL (Transact-SQL), Python, Snowflake, C, PHP, XML

  • Tools

    Cron, Toad, Spotfire, Amazon Athena, Microsoft Access, AWS Glue, MySQL Performance Tuning, BigQuery, Teradata SQL Assistant, Informatica ETL, DbVisualizer, Erwin, Turbo Pascal, Excel 2013, Subversion (SVN), Git

  • Paradigms

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

  • Platforms

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

  • Storage

    Database Architecture, DB, Database Modeling, Databases, SQL Stored Procedures, Relational Databases, Database Transactions, Database Triggers, Data Pipelines, Oracle SQL, Oracle 12c, PL/SQL, Oracle RDBMS, SQL Performance, Database Performance, Vertica, Netezza, Oracle PL/SQL, MySQL, Microsoft SQL Server, PostgreSQL, Database Administration (DBA), SQL Server 2017, Redshift, Oracle Multitenant, MongoDB, Amazon S3 (AWS S3), Azure SQL, Teradata, SQL Server DBA, MariaDB, Database Lifecycle Management (DLM), Cassandra, MemSQL, SQL Server Integration Services (SSIS), Amazon Aurora, SQL Server 2005, Dynamic SQL

  • Other

    Informatica, Star Schema, Data Engineering, Database Optimization, Database Table Optimization, Query Optimization, Data Warehouse Design, Stored Procedure Tuning, Stored Procedure Refactoring, Big Data, Data Architecture, Architecture, ETL Pipelines, PL/SQL Tuning, Performance Tuning, ETL Development, Data Warehousing, Data Modeling, Data Analysis, Complex Data Analysis, Data Cleaning, Data Cleansing, Data Migration, Reverse Engineering, Data Analytics, Database Schema Design, Reporting, Integration, Data Management, Data Marts, Debugging, Electronic Data Interchange (EDI), ETL Tools, Google BigQuery, Computer Science, Mathematics, Physics, Data Auditing, Apache Cassandra, Oracle OEM 12c, Analytics, Big Data Architecture, SingleStore, Microsoft Data Transformation Services (now SSIS), Data Build Tool (dbt), Partitioning, Relational Database Design, Oracle Forms & Reports, Snowpipe, Data Loading, SQL Server 2019, Indexing

  • Frameworks

    Presto DB, ASP, .NET

  • Libraries/APIs

    Pandas

Education

  • 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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