Eugene Bereznuk, Developer in Geraardsbergen, Belgium
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Eugene Bereznuk

Verified Expert  in Engineering

SQL Developer

Geraardsbergen, Belgium
Toptal Member Since
July 5, 2021

Eugene is an SQL Server expert with more than 25 years of experience in Microsoft SQL Server, from version 6.5 to the most recent versions, which are standalone and cloud-based. He's worked for small businesses as well as global enterprises like Kone, DHL, and Sony. He also held courses in "data and database architecture" and "the technical side of SQL Server" for classes of up to 10 people. Eugene is familiar with most SQL monitoring packages and is an expert in Red Gate software.


Azure SQL Databases, Database Administration (DBA), Data, Database Development...
Objecutive, Inc
SQL, Microsoft SQL Server, Performance Tuning, Optimization...
Azure SQL Databases, SQL Server DBA, SQL Server 2016, Optimization...




Preferred Environment

Windows, SQL, Azure SQL Databases, SQL Server DBA, Microsoft SQL Server

The most amazing...

...moment I've had is with an SQL query that used to take 4-5 hours to complete suddenly executed in 14 seconds, all due to corrected indexes and a query hint.

Work Experience

SQL Server Consultant

2023 - 2024
  • Conducted an analysis and audit of existing data import, ETL processes, and data correlation.
  • Conducted a functional analysis of existing databases and data model alterations.
  • Refactored the code, improved performance, and implemented testing and production.
Technologies: Azure SQL Databases, Database Administration (DBA), Data, Database Development, Data Modeling, JSON

MS SQL Performance Tuning Consultant

2023 - 2024
Objecutive, Inc
  • Identified several scopes (landscapes) of performance improvements, starting with global Windows/SQL Server settings and options, via generic data model improvements up to individual processes and databases.
  • Identified the most critical bottlenecks across all databases.
  • Developed the proof of concept by refactoring the code of many procedures, views, and functions and adjusting the index system.
Technologies: SQL, Microsoft SQL Server, Performance Tuning, Optimization, Database Optimization, Data Migration

SQL Server Specialist

2022 - 2022
  • Handled the auditing of existing SQL Server databases and data flows.
  • Identified performance bottlenecks and potential risks.
  • Implementation of system versioning technologies instead of homemade history tables for a data audit.
Technologies: Azure SQL Databases, SQL Server DBA, SQL Server 2016, Optimization, Performance Tuning, Database Optimization, JSON, Excel VBA

SQL Server DBA | Performance Expert

2021 - 2022
  • Merged two multi-billion rows tables. The total downtime required was one hour.
  • Identified non-used indexes and implemented numerous changes to the index system, which significantly improved performance in certain cases.
  • Straight-lined backup processes and tweaked Lungren's procedures for full and differential backups.
Technologies: SQL Server 2016, Data, SQL, SQL Performance, Database Performance, Microsoft DBA, Optimization, Performance Tuning, Database Optimization, JSON, Microsoft Excel, Excel VBA, Data Migration

SQL Server Specialist | Support Coordinator

2020 - 2021
  • Administered the SQL Server administration managing various environments, stored procedures, functions, jobs, indexing, partitioning, replication, mirroring, resource management, performance analysis, and improvements.
  • Handled massive data migrations, including sources like multiple Oracle databases, flat files, etc. Did a post-migration data audit.
  • Designed, developed, and implemented a data import and integration engine.
Technologies: SQL Server 2016, Microsoft SQL Server, Database Optimization, JSON, Data Migration

Global SQL Server Database Administrator (DBA) | Senior Data Expert

2013 - 2020
  • Performed SQL Server administration, including but not limited to stored procedures, functions, jobs, indexing, partitioning, replication, mirroring, resource management, performance analysis, and improvements; also monitored the SQL Server.
  • Developed, designed, and architected data warehouses which included the design, planning, and implementation of a range of environments design (production, acceptance, development); also helped to migrate platforms.
  • Contributed to software architecture primarily the data flow and persistence.
Technologies: SQL Server 2008 R2, SQL Server Integration Services (SSIS), SQL Server 2016, Azure SQL Databases, Redgate SQL Toolbelt, Database Design, Database Performance, Microsoft SQL Server, SQL Server DBA, Optimization, Performance Tuning, Database Optimization, Microsoft Excel, Excel VBA, Data Migration

SQL Server Engineer

2012 - 2012
DHL International
  • Analyzed the existing enterprise datastore and BI data warehouses and designed, modeled, and prepared the migration to another infrastructure; also implemented the actual migration.
  • Evaluated the existing SSIS ETL structure and analyzed the existing OLTP processes.
  • Optimized, maintained, and administered the corporate databases and data warehouses.
Technologies: SQL Server 2008 R2, SQL Server 2012, Windows PowerShell, Microsoft SQL Server, Microsoft Excel, Excel VBA, Data Migration

Data Architect | SQL Engineer

2009 - 2011
Belgacom (now Proximus)
  • Architected and physically installed the SQL Server clustered environment and new and existing data centers.
  • Audited and optimized existing data centers and databases, including massive performance improvements.
  • Designed and implemented the Microsoft BI environment which included the development and administration of the data and Infrastructure migration and consolidation design, planning, and implementation.
Technologies: SQL Server 2005, SQL Server 2008 R2, SQL Server Integration Services (SSIS), ER/Studio Data Architecture, Windows PowerShell, Database Design, Data Architecture, Database Architecture, Microsoft SQL Server

Database Engineer | SQL Server Performance Specialist | Database Administrator (DBA)

2008 - 2009
Sony Electronics
  • Analyzed the existing SAN/Cluster SQL Server instances which included the preparation and implementation of the migration from 2000 to 2005 versions.
  • Created a new data warehouse and designed and developed ETL processes.
  • Solved performance issues and tracked and enhanced critical processes.
Technologies: SQL Server 2000, SQL Server 2005, SQL Server 2008 R2, DTS, SQL Server Integration Services (SSIS), Redgate SQL Compare, ER/Studio Data Architecture, Database Design, Database Performance, Microsoft SQL Server, SQL Server DBA, Optimization, Data Migration

Migration of Chinese Corporate Databases

When I started on this project, I found old corporate databases in multiple formats, including SQL Server 2000 to 2008, Oracle, etc. The Chinese encoding was different everywhere (including outdated and archaic encodings) and needed to be unified to UTF-8. The approximate volume of data was close to 2.5-3TB. The target platform was SQL Server 2016 cluster, and the allowed downtime was 12 hours. After downtime, every hour of data unavailability would cost the company millions.

To save time, data streams were processed consequently for encoding, quality and integrity. A portion of data was preloaded into staging tables.

The project was finished successfully, with the indexes and replication created well within the downtime frame.

Data Export to S3

It was necessary to regularly export data (with preliminary processing) to a cloud-landing site. The source data was scattered among multiple databases and data warehouses, often requiring dozens of complicated joins.

We created numerous stored procedures which provided processed and formatted data. A fully dynamic SSIS package accepted a stored procedure name as one of the parameters, executed it, exported the results into a CSV file, and placed them on target landing site—all fully automatically, without any intervention.

Performance Improvement at a Global Corporation

A global multinational corporation had a portion of its technical, online, and archive data on a vast array of SQL Servers all around the globe. This data was used in reporting as well as exporting to SAP and other systems.

The performance was deteriorating as the data volume and traffic increased.
The preliminary stage included isolating the most problematic queries, triggers, functions, and stored procedures. Also, about 50% of the queries were generated automatically by third-party software and could not be altered.

To solve this, we performed a global audit of the index system which resulted in removing excessive and unused indexes with changing the majority of the existing indexes to newly created ones.

Where possible, function calls were removed from clauses, triggers replaced with external code, and isolation levels and degrees of parallelism were reviewed.

We chose to implement SQL Server Resource Governor to separate system resources between different applications and users. As a result performance problems disappeared completely while guaranteeing future scalability and expandability.


Redgate SQL Compare, SQL Server Profiler, Microsoft Excel, Microsoft Access, DTS, Microsoft Power BI


T-SQL (Transact-SQL), Visual Basic 6 (VB6), SQL, Snowflake, Stored Procedure, Excel VBA, Visual Basic for Applications (VBA)


Database Design, ETL, Database Development, Business Intelligence (BI)




SQL Server DBA, Database Architecture, Redgate SQL Toolbelt, Database Performance, SQL Performance, Data Definition Languages (DDL), SQL Server 2008 R2, SQL Server 2016, SQL Server 2012, SQL Server 2005, SQL Server 2000, SQL Server 2019, Microsoft SQL Server, DB, SQL Stored Procedures, Databases, Database Migration, Database Replication, Relational Databases, Database Mirroring, SQL Architecture, Database Administration (DBA), Microsoft DBA, SQL Server Integration Services (SSIS), JSON, Azure SQL Databases, ER/Studio Data Architecture, SQL Server 2014, SQL Triggers


Windows PowerShell


Data Warehouse Design, Data, Relational Database Design, Key Performance Indicators (KPIs), Optimization, Performance Tuning, Database Optimization, Data Migration, Data Architecture, Data Warehousing, Data Engineering, Data Modeling, Consolidation, Indexing, Encoding

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