Віталій

Vitalii Martyniuk
Data Engineer
[відкрити контакти](див. вище в блоці «контактна інформація») [відкрити контакти](див. вище в блоці «контактна інформація») [відкрити контакти](див. вище в блоці «контактна інформація»)
Kyiv, Ukraine

SUMMARY
Data Engineer with 7 years of software engineering experience, including 4 years focused on Data Engineering. Specialized in distributed
data processing and building analytical platforms on AWS using Python/PySpark, AWS Glue, Apache Iceberg, and Redshift. Experienced in
lakehouse architectures, incremental data processing, analytical data models, reporting solutions, and SQL performance optimization, with a
strong C#/.NET backend background.

KEY ACHIEVEMENTS
Reusable ETL Framework SQL Performance Optimization
Designed a shared ETL framework with reusable Reduced redundant data materialization and controlled
Python/PySpark handlers for parameterized processing and intermediate dataset growth in complex SQL workloads
loading into multiple data stores and shared the approach through reusable results and batch processing.
with the team for reuse across data workflows.

Backend & Data Engineering .NET Licensing System
Expanded from C#/.NET backend development into Built and launched an internal licensing application from
production data engineering, delivering Python/PySpark scratch, covering architecture, database design, REST APIs
pipelines on AWS while continuing to build backend services. and the administration interface.

EXPERIENCE
Data Engineer
Trinetix
02/2023 - Present
Enterprise AWS lakehouse built on Amazon S3 and Apache Iceberg, following a medallion architecture to deliver curated data marts for
company, ownership and financial analytics.
• Reporting engine. Drove the end-to-end design and delivery of a dynamic SQL reporting engine driven by JSON templates, making
technical decisions around query generation, Redshift aggregation pushdown, role-based filtering, pagination, caching and exports.
Reduced reporting query execution cost by approximately 40% through SQL tuning under a strict 30-second query limit
• Company hierarchies. Implemented iterative Redshift SQL calculations over company relationship graphs, reusing calculated subtrees to
prevent intermediate dataset explosion caused by duplicated descendants across multiple roots. Optimized execution with staged joins,
distribution and sort keys, and hash-based batching to control intermediate dataset growth, with results returned to Iceberg for portfolio
analytics
• Entity-level delta tracking. Developed timestamp-based change detection across related datasets, mapping changes to affected
companies for selective batch recomputation instead of full dataset rebuilds. Used entity-scoped keys and hash comparisons to apply
inserts, updates, and deletions while preserving results for unaffected companies
• Reusable ETL framework. Owned the design and implementation of table-specific Python/PySpark handlers within a parameter-driven
AWS Glue framework, supporting sequential execution of multiple processing steps in a shared Spark session and reusable loading
components for Aurora PostgreSQL, OpenSearch and Redshift
• Engineering practices and collaboration. Contributed to technical design discussions with developers and architects, reviewed pull
requests, shared and demonstrated reusable implementation approaches, and introduced repository-level Git hooks to validate AWS
Step Functions definitions and Python jobs before review and CI, catching validation issues earlier in the development workflow
• Lakehouse pipelines and orchestration. Built multi-stage ingestion and transformation pipelines delivering curated Iceberg/Parquet
datasets on Amazon S3. Orchestrated AWS Glue jobs and Lambda functions with Step Functions, managing dependencies, retries,
failures, and execution flow across pipeline stages
• Cross-layer delivery. Delivered end-to-end features from data preparation to backend APIs, implementing data pipelines and C#/.NET
Lambda functions that queried OpenSearch and exposed analytical data through GraphQL via AWS AppSync

Backend Engineer
Trinetix
05/2021 - 02/2023
Enterprise OLTP workplace platform for meeting-room and desk booking across multiple offices and time zones, built on a .NET
microservices and event-driven architecture.
• Backend development. Developed C#/.NET REST APIs and backend services for booking and workplace resource management,
including SQL Server stored procedures and data access through a custom ADO.NET-based framework. Implemented data modification
logic using MERGE operations and worked with application flows spanning API, business logic and persistence layers
• Microservices and messaging. Maintained asynchronous CQRS data flows through Azure Service Bus and diagnosed cross-service
synchronization failures by tracing messages and state changes between write operations and downstream read models
• API and platform evolution. Contributed to the migration from REST to GraphQL with Hot Chocolate, adapting existing backend
functionality and data access flows to the new API model. Wrote unit and integration tests and ran and debugged microservices locally
using Azure Service Fabric to reproduce cross-service scenarios

EXPERIENCE
Full Stack Engineer
Hideez Group Inc
12/2019 - 05/2021
• Backend and administration portal. Developed ASP.NET Core REST APIs and Blazor Server components for an enterprise identity and
access management platform, covering employee and device management, access policies, password resets, OTP and passwordless
authentication. Integrated backend functionality with the desktop client and enterprise authentication flows
• Licensing and identity services. Designed and built an internal licensing service from scratch, including the domain model, MySQL
schema, Entity Framework Core data access, REST APIs, license lifecycle, and cryptographic signing and verification. Implemented
directory and authentication integrations using Active Directory/LDAP, FIDO2/WebAuthn and SAML 2.0

Backend Engineer
IT-Enterprise
10/2019 - 12/2019
• CRM and platform development. Contributed to the CRM module of an enterprise ERP platform using C# and ASP.NET MVC,
implementing and maintaining functionality for leads, accounts, contacts, opportunities, product catalog and reporting. Worked with the
platform’s internal C# data-access API and MS SQL for querying, updating and troubleshooting business data

SKILLS
Programming & Query Languages
Python, SQL / T-SQL, C#, JavaScript

Data Processing & Lakehouse
Apache Spark / PySpark, AWS Glue, Amazon S3, Apache Iceberg, Parquet, AWS Glue Data Catalog, AWS Step Functions, AWS
Lambda, AWS EventBridge, AWS SQS, Azure Service Bus

Data Engineering
ETL / ELT, Distributed Data Processing, Data Lake / Lakehouse, Medallion Architecture, Incremental Processing, Data Modeling,
SCD1/2/3, Data Marts, OLAP, Data Warehouse, SQL Performance Tuning

Databases, Analytics & Search
SQL Server, PostgreSQL, MySQL, Amazon Redshift, Aurora PostgreSQL, DynamoDB, AWS Athena, OpenSearch

Backend & APIs
.NET, ASP.NET Core, Entity Framework Core, ADO.NET, REST, GraphQL, AWS AppSync, Microservices, Event-Driven Architecture

Development & Testing
Git, Azure DevOps + CI/CD, Docker, pytest, xUnit, MSTest, Unit & Integration Testing

EDUCATION
Bachelor's degree, Economics, Management and Psychology
State University of Trade and Economics
09/2019 - 12/2022

Software design and development
IT STEP Computer Academy
07/2017 - 12/2020

LANGUAGES
English B2 Ukrainian Native Russian Fluent