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greg_zapantis

Grigoris Z

@greg_zapantis

NET Backend Architect and SQL Server ETL Expert

Greece
English
About me
I build .NET backends and reliable data platforms, backed by 20 years of engineering experience. Services include C# and ASP.NET Core APIs, SQL Server tuning, SSIS and custom ETL, data integration, and warehouse modelling. My experience includes ClickHouse and StarRocks analytics warehouses, Kafka ingestion, and Prefect orchestration across financial services, insurance and media. I focus on maintainable code, data quality, reconciliation and measured performance. Message me to define a clear scope.... Read more

Skills

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greg_zapantis
Grigoris Z
Offline • 

See my services

Design & Optimization
I will analyze and optimize sql server queries and indexes
From$70 / projectMore details
API & Integrations
I will build or improve c sharp asp net core backend apis
From$70 / projectMore details

Portfolio

Work experience

Cepal_Hellas Financial Services SA

Independent Contractor / Technical Lead

Cepal Hellas Financial Services SA

May 2023 - Present • 3 yrs 6 mos

Lead engineering on a metadata-driven platform consolidating operational systems into a unified SQL Server data store. Designed C#/.NET loading and SSIS orchestration, source reconciliation and temporal history. Built ASP.NET Core APIs and versioned integration clients. Tuned queries and indexes using before/after execution plans and output-equivalence checks.

buffermusic

Co-founder and Independent Contractor - Data Platform

buffermusic

Apr 2023 - Present • 3 yrs 7 mos

Build and operate data pipelines and a ClickHouse warehouse for a music and media intelligence platform. Develop Python/Prefect ETL with full and incremental synchronization, checkpoint recovery, retries and concurrency controls. Build C#/.NET ingestion services, reusable Dapper and MongoDB data-access libraries, and metadata-driven loading with parallel execution and ClickHouse bulk loading. Work across MySQL/Percona, MongoDB and ClickHouse to support analytics and reporting.

Hellas_Direct

Data Platform Architect / Senior .NET Engineer

Hellas Direct

Oct 2019 - Apr 2023 • 3 yrs 6 mos

Designed and built a multi-country data platform for an insurance business. Developed a custom C#/.NET ETL framework, dimensional warehouse models, Kafka ingestion and automated source-to-warehouse reconciliation. Integrated MongoDB, AWS DocumentDB and PostgreSQL sources with MariaDB staging and ClickHouse/StarRocks analytics. Managed schema migrations across development, test and production.