Publication
Solving Bottlenecks With SQL Indexes and Partitions
https://www.toptal.com/developers/database/sql-indexes-explained-pt-3
Mirko is currently unavailable
Mirko Marović
Verified Expert in Engineering
Database Engineer and Developer
Prague, Czech Republic
Toptal member since March 2, 2020
Bio
Mirko has more than 20 years of experience in database design, development, and optimization. He's worked with the most used database platforms: MS SQL Server, Oracle, MySQL, and PostgreSQL. He's optimized database queries, indexes, and settings for databases with extreme workloads. As a data engineer, Mirko has also designed and developed data warehouse solutions for customers in the US, Russia, Czech Republic, Germany, Norway, Serbia, and Bosnia.
Portfolio
Top For Sport s.r.o.
Azure SQL, ADF, Microsoft Power BI, Data Modeling, Database Design...
Cross Masters
Database Development, Database Modeling, ETL, Azure SQL...
BetSys
Database Development, Database Modeling, Indexing, PostgreSQL, Git, Jira...
Experience
- Performance Tuning - 15 years
- Database Development - 15 years
- Data Modeling - 10 years
- Microsoft SQL Server - 8 years
- Oracle PL/SQL - 7 years
- PostgreSQL - 5 years
- ETL - 4 years
- Azure SQL - 2 years
Preferred Environment
PostgreSQL, MySQL, Oracle, Microsoft SQL Server, Data Modeling, Azure Data Factory (ADF), Azure SQL
The most amazing...
...performance improvement I've achieved was redesigning a query generator accessing tables with billions of rows, improving performance 12 to 80 times.
Work Experience
Senior Data Quality Manager
2023 - PRESENT
Top For Sport s.r.o.
- Established database best practices and standards, leading to a 60% reduction in report inconsistency tickets.
- Refactored master sales pipelines, data marts, and PBI reports that reduced refresh time from one hour to two minutes.
- Refactored the data model of stock and sales reports, enabling fast and reliable data refresh. Established a partitioning schema, keeping data volume under agreed limits.
Technologies: Azure SQL, ADF, Microsoft Power BI, Data Modeling, Database Design, Database Modeling, ETL, Azure Data Factory (ADF), Database Development, Database Optimization, Data Integration
Senior Database Engineer
2022 - 2023
Cross Masters
- Redesigned the CIMEX financial data mart to achieve reliable and consent data load multiple times daily.
- Reduced load time for various financial reports by data model design introducing star schema with outriggers and role-playing dimensions.
- Trained data engineers in SQL development best practices.
Technologies: Database Development, Database Modeling, ETL, Azure SQL, Azure Data Factory (ADF), Databases, SQL, Database Design, Indexing, Transact-SQL (T-SQL), Data Modeling, Git
Senior Database Engineer
2019 - 2022
BetSys
- Optimized PL/pgSQL and SQL functions and indexes before the EU soccer championship, reducing overall CPU load by 60%.
- Redesigned the indexes on payment-related tables, reducing data reads by 40%.
- Reduced ticket evaluation for big matches (200,000+ tickets) from 40 minutes to less than 2 minutes.
Technologies: Database Development, Database Modeling, Indexing, PostgreSQL, Git, Jira, Databases, SQL, Database Design, PL/pgSQL, Performance Tuning
Senior Database Specialist
2009 - 2019
Self-employed
- Developed and optimized MySQL query generation patterns for a financial services provider. Improved query performance 12 to 80 times from the previous version.
- Developed SQL Server stored procedures and triggers for Faraj Fund, UAE.
- Built PostgreSQL functions and optimized queries and indexes for TV Nova, Czech Republic.
- Created the scheduling algorithm and the database model and developed MySQL queries for the 3v3 football tournaments portal, Phoniax, Norway.
- Designed and developed an SQL Server reporting database for Blue Rabbit, DKNY's exclusive distributor in Prague, Czech Republic.
- Designed a POS application for Blue Rabbit in the Czech Republic.
- Developed Oracle PL/SQL packages of data synchronization between provisioning and billing systems for MTS, a telecom operator in Serbia.
Technologies: PostgreSQL, MySQL, Oracle, Microsoft SQL Server, Databases, SQL, Database Design, PL/pgSQL, Database Optimization, Performance Tuning, Indexing, Transact-SQL (T-SQL), Data Modeling, Jira, ETL
Quality Assurance Manager
2007 - 2009
SitronicsTS, Prague, Czech Republic
- Managed the quality assurance department, including test analysis, test execution, test automation, test data preparation, integration testing, and performance testing teams.
- Participated in the design and establishment of SDLC and QA processes.
- Managed product testing of various telecom OSS/BSS deliveries in Russia, Czech Republic, Germany, Uganda, and Serbia.
Technologies: TFS
Consultant
2005 - 2006
Time Import, Prague, Czech Republic
- Gathered and manage requirements for KUSCK, Czech Republic.
- Deployed, configured, and managed the subversion version control system.
- Designed high-level architecture of KUSCK customer portal back-end.
Technologies: Subversion (SVN)
Database Engineer
2003 - 2005
Tmp Worldwide (Monster), Maynard (USA), Prague Czech Republic
- Developed stored procedures for a campaign management data mart.
- Reviewed code and trained more than 40 developers in T-SQL best practices.
- Designed indexes and optimized stored procedures for job seekers, employers, and mass sender subsystems.
Technologies: IBM Rational ClearQuest, Embarcadero RAD Studio, Microsoft SQL Server, Databases, SQL, Database Design, Database Optimization, Performance Tuning, Indexing, Transact-SQL (T-SQL), SQL Server 2000, Data Modeling
Oracle Consultant
2003 - 2003
Ad Astra, Prague, Czech Republic
- Developed PL/SQL packages implementing Wholesales Billing API for GTS (telecom operator), Czech Republic.
- Designed the logical and physical model for GTS Wholesales Billing.
- Introduced unit testing for PL/SQL stored procedures and functions inside PL/SQL packages.
Technologies: Databases, SQL, Oracle PL/SQL, PL/SQL, Indexing, Oracle, Data Modeling
Database Team Leader
1999 - 2002
Strom Telecom, Doubravice, Czech Republic
- Designed, developed, optimized, and administered massive telecom databases for clients in Russia, Czech Republic, and Germany.
- Designed the database model of wholesales billing and least cost routing for Callax and Dusseldorf, Germany.
- Migrated the telecom billing system from SQL Server to Oracle.
- Implemented central ODS of telecom billing for MGTS, Moscow.
Technologies: Visual Basic 6 (VB6), SQL Server 2000, Databases, SQL, Database Design, Oracle PL/SQL, PL/SQL, Database Optimization, Performance Tuning, Indexing, Transact-SQL (T-SQL), Oracle, Data Modeling, ETL
Experience
Redesign Sales Data Mart for 11 Team Sports
The data analytics team uses sales data mart to gain insights to manage and improve sales. The redesign achieved better data integration, providing more reliable data and information while reducing incidents. It also allows more frequent data refresh and faster load of Power BI reports.
Ticket Evaluation Optimization
Main Betsys's product is an online betting system. Currently, the biggest deployment is in Poland for betting provider STS. The slowness of ticket evaluation was the major competitive disadvantage. Evaluating big matches with more than 200 tickets took more than 40 minutes. After performance optimization, it only takes up to two minutes.
Query Engine for Financial Market Data
I was responsible for redesigning MySQL query patterns used for built-in data tracking tools. The query engine returns 20 years of data with minute granularity. I reduced query execution time by 12-80 times for various query patterns.
FORIS - OSS/BSS System for MTS, Moscow
https://moskva.mts.ru/personalFORIS is an OSS/BSS system consisting of billing, rating, provisioning, and resource inventory modules using massive Oracle databases with hundreds of millions of CDR rows loaded each hour. As a database team leader, I was responsible for designing the data model, PL/SQL development, database administration, and performance optimization. The system was successfully deployed, handling trillions of CDR data, inventory of hundreds of millions of cell phones, and other mobile devices and generates monthly invoices for 100 million subscribers.
Portal for Job Seekers
Job Seekers portal pages received on average 8,000 hits per second at the time I was working for Monster as a database engineer. I participated in defining and enforcing SQL Server standards and best practices. My tasks included code review, design review, and performance optimization. I was responsible for T-SQL stored procedures code review produced by more than 40 developers located in Prague, Czech Republic, and Maynard, Massachusets, USA.
PERSON Redesign for TV Nova, Czech Republic
PERSON is a user management system used by TV Nova web and Voyo streaming users. I was responsible for PL/pgSQL development, testing, reporting, and query performance optimization, including PostgreSQL indexes redesign.
Education
1982 - 1989
Master's Degree in Computer Science on the Faculty of Mathematics
University of Belgrade - Belgrade, Serbia
Skills
Tools
TFS, Subversion (SVN), IBM Rational ClearQuest, Git, Jira, Microsoft Power BI
Languages
Transact-SQL (T-SQL), PL/pgSQL, SQL, Visual Basic 6 (VB6), Python 3
Paradigms
Database Development, Database Design, ETL
Storage
SQL Server 2000, PostgreSQL, Database Modeling, Microsoft SQL Server, Databases, MySQL, Oracle PL/SQL, PL/SQL, Azure SQL, Data Integration
Platforms
Oracle, Azure SQL Data Warehouse
Frameworks
ADF
Other
Database Optimization, Performance Tuning, Indexing, Data Modeling, Embarcadero RAD Studio, Azure Data Factory (ADF), Data Warehouse Design, Data Warehousing
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