Денис

Denys Farafonov
Backend Developer / Integration Engineer
SQL Server | Oracle | REST APIs | Backend Development

Spain (open to remote)
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SUMMARY

Backend and Integration Engineer with 10+ years of experience working with database-driven systems,
REST APIs, system integrations, and backend business logic.

Strong background in Oracle and MS SQL Server, including complex SQL, stored procedures, data
processing, performance optimization, and integration with external services.

Experienced in building backend workflows, API integrations, automation, and production solutions for
business-critical systems. Comfortable working with existing code, investigating problems, and using AI
tools to accelerate development while reviewing and validating generated code.

Currently expanding practical experience with Python and modern backend development.

KEY ACHIEVEMENTS

Reduced execution time of a high-load pricing query by 70–80% by refactoring Oracle SQL logic
using CTEs
Designed and implemented an automated returns processing system integrating with Nova Poshta
API
Restored system functionality within one day after breaking changes in an external Prom API
Built a monitoring system for background services, enabling proactive failure detection and
improving system reliability

PROFESSIONAL EXPERIENCE

Backend / Integration Engineer (MS SQL Server)

SMARTY UA (Ukrainian distributor of children's products) | Feb 2025 – Present

Develop and maintain backend logic for business-critical operations using MS SQL Server
Develop and maintain integrations with external REST APIs, including Nova Poshta and Prom
Build backend automation workflows for data processing and business operations
Process JSON payloads and implement business rules for API-driven workflows

Key Contributions:

Designed and implemented an automated returns processing system integrating with Nova Poshta
API, reducing manual processing and improving operational efficiency
Built backend services for handling external API data and automating business workflows
Developed a monitoring system for background services, detecting repeated failures (2+
consecutive errors) and triggering alerts
Rapidly adapted backend logic to breaking changes in the external Prom API, rewriting MS SQL
procedures within one day to restore system functionality
Implemented backend logic for a B2B bonus system, processing JSON payloads and dynamically
adding bonus items to orders based on business rules
Designed API key lifecycle monitoring for Nova Poshta, including expiration tracking and automated
notifications

Database Engineer / Backend Developer (Oracle)

ISD Information Systems (partner of SCC Soft Computer, healthcare software solutions) | 2020 – Present

Designed and optimized complex SQL queries, stored procedures, and packages in Oracle DB
Improved database performance using indexing strategies and execution plan analysis
Worked with high-load datasets containing millions of transactions
Developed and maintained backend data processing logic for business-critical systems
Collaborated with business and engineering teams to improve data workflows and reporting

Software Developer

ISD Information Systems (partner of SCC Soft Computer, healthcare software solutions) | 2018 – 2020

Maintained and enhanced legacy systems using C++, PL/SQL, and enterprise tooling
Worked with multithreading and system-level logic
Supported backend components and data processing pipelines
Used SVN and worked in Unix/AIX environments

Embedded Software Engineer

Space Systems Engineering Ukraine | 2016 – 2017

Developed onboard control software using C/C++ on Linux-based systems
Worked with embedded systems, including Raspberry Pi, resource management, and system-level
programming
Used Git for version control

Backend Developer / Integration Engineer

BaDM Ltd (large pharmaceutical distributor) | 2012 – 2016

Developed and maintained backend systems using Oracle DB, PHP, and REST APIs
Implemented business logic via stored procedures and backend services
Optimized database performance for large-scale internal systems
Supported internal web applications and backend integrations

Business Analyst (IT Department)

BaDM Ltd (large pharmaceutical distributor) | 2011 – 2012

Collected and formalized technical requirements
Participated in software validation and quality control

Analyst (Sales Department)

BaDM Ltd (large pharmaceutical distributor) | 2008 – 2010

Performed data analysis, including ABC/XYZ analysis
Optimized delivery routes and sales forecasting

TECHNICAL SKILLS

Backend & Integration

REST APIs, Webhooks, API Integration
Backend business logic and data processing
JSON processing
External service integrations
API troubleshooting and maintenance

Databases

Oracle (PL/SQL), MS SQL Server
Complex SQL, stored procedures
Query optimization, indexing, execution plans

Programming

Python (basic practical experience, currently developing)
C++, C#, JavaScript, PHP

AI-Assisted Development

ChatGPT — primary AI tool for coding, debugging, code analysis, refactoring, SQL optimization,
and technical problem solving
Claude / Claude Code — code assistance, analysis, and technical documentation
Gemini — quick technical research, documentation lookup, and comparison of alternative
approaches
Reviewing, validating, and adapting AI-generated code

Tools & Environment

Git, SVN
Linux/Unix

Languages

English (B2)
Spanish (basic, in progress)
Russian (fluent)
Ukrainian (fluent)

EDUCATION

Master’s Degree in Computer Science
National University of Dnepropetrovsk