Valerii Konchin, Developer in Vancouver, BC, Canada
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Valerii Konchin

Software Engineer and Developer

Vancouver, BC, Canada

Toptal member since February 11, 2026

Bio

Valerii is a Java back-end engineer with 20 years of experience building high-load, fault-tolerant cryptocurrency exchanges and trading platforms. He specializes in Spring Boot microservices, blockchain integrations, low-latency processing, Kubernetes, AWS, and CI/CD automation. He has independently shipped macOS and iOS apps to the App Store, owning the full lifecycle from architecture to release. Valerii thrives where one engineer takes full ownership from design through production.

Portfolio

Mercor
AI Model Training, AI Prompts, Java, Java SE (Core Java), Dart...
Self Employed
MacOS, AppStore, Swift, SwiftUI, Dart, Flutter, Artificial Intelligence (AI)...
Roaming Reflections
DSLR Photography, Photoshop CC, Adobe Lightroom, Capture One, Color Grading...

Experience

  • Linux - 20 years
  • Java - 20 years
  • REST APIs - 20 years
  • Multithreading - 20 years
  • Microservices - 10 years
  • Docker - 10 years
  • Spring Boot - 10 years
  • Blockchain - 8 years

Preferred Environment

MacOS, Linux, IntelliJ IDEA, Visual Studio Code (VS Code), Bash, Slack, Machine Learning, Data Science

The most amazing...

...solution I've built is Renzu Select, a pro photo culling app for macOS, with on-device ML and RAW support.

Work Experience

Software Engineer (Independent Contractor)

2026 - PRESENT
Mercor
  • Contributed to AI-focused projects across varying project scopes and requirements.
  • Completed complex software engineering tasks across large-scale codebases in an AI-assisted environment, serving as a technical benchmark contributor for a confidential model evaluation program.
  • Assessed AI agent outputs across multi-turn coding sessions, identifying behavioral issues and providing structured preference rankings to inform improvements in code generation models.
Technologies: AI Model Training, AI Prompts, Java, Java SE (Core Java), Dart, Large Language Models (LLMs), Codex, Claude, SSH, XML

Software Developer

2026 - PRESENT
Self Employed
  • Designed and shipped production macOS and iOS applications as a solo developer, owning the full lifecycle from architecture and implementation to App Store release.
  • Defined an offline-first application architecture prioritizing privacy, local data processing, and zero cloud dependency, deliberately avoiding unnecessary client-server complexity.
  • Applied the KISS principle when designing application architecture, choosing simple and maintainable local system designs instead of service-based architectures where they were not required.
  • Analyzed professional photography workflows and designed tools to significantly accelerate the photo selection process, enabling users to review and select thousands of images with minimal interaction.
  • Built a machine learning pipeline for visual similarity detection using vector embeddings and clustering to automatically group related images in large photo collections.
  • Implemented on-device AI capabilities using Apple Foundation Models to extract and structure information from images and web content without relying on external services.
  • Engineered high-performance media processing workflows capable of handling thousands of RAW files per session while optimizing disk I/O, memory consumption, and application responsiveness.
  • Developed domain-specific data normalization systems enabling automatic deduplication, aggregation, and unit conversion across multiple datasets.
  • Designed resilient processing pipelines using asynchronous execution, background processing, and caching strategies to support large-scale local data processing.
  • Made strategic product decisions to accelerate delivery, focusing development on macOS first and postponing cross-platform support to reduce complexity and reach a production release faster.
Technologies: MacOS, AppStore, Swift, SwiftUI, Dart, Flutter, Artificial Intelligence (AI), Neural Networks, RevenueCat, Software Architecture, Infrastructure as a Service (IaaS), Claude, Codex, Large Language Models (LLMs), AI Model Training, AI Prompts, Test Automation, Debugging, SSH, XML

Founder & Event/Portrait Photographer

2023 - PRESENT
Roaming Reflections
  • Photographed automotive and motorcycle events across Vancouver, delivering edited galleries within 24 hours of the shoot.
  • Covered fashion, rodeo, and concert events, producing portfolio-ready images for clients and personal brand projects.
  • Shot product and apparel photography for Lords of Gastown, creating commercial-quality visuals for retail use.
  • Conducted portrait and model sessions, building a diverse portfolio spanning lifestyle, fashion, and personal branding.
  • Developed Renzu Select and Renzu Flow—proprietary photo culling and RAW processing tools that cut post-production time to under 24 hours.
Technologies: DSLR Photography, Photoshop CC, Adobe Lightroom, Capture One, Color Grading, Renzu Select, Event photography, Corporate headshots, Fashion photography, Editorial photography, Automotive/motorsports, Portrait & model photography, Sports photography, Headshots, Photoshoot Production, Photography

Senior Software Engineer

2021 - 2025
GMO-Z.com Fintech CA (Cardinalchain)
  • Architected and implemented cryptocurrency blockchain integrations for seven chains, including transaction flows, wallet management, signing infrastructure, and reconciliation logic.
  • Built a multi-signature transaction signing system with configurable N-of-M threshold schemes using air-gapped signing nodes for enhanced security.
  • Developed Ethereum smart contracts in Solidity, implementing a multi-signature wallet with dynamic threshold configuration.
  • Optimized Java 8 microservices for low-latency trading operations through JVM tuning, including GC optimization, heap profiling, and thread pool configuration.
  • Developed REST APIs and back-end services for a cryptocurrency trading platform using Spring Boot and Hibernate.
  • Fixed critical production issues in trading services, including transaction boundary problems, database connection pool misconfigurations, and memory leaks.
  • Reduced CI/CD pipeline runtime from 12 hours to two hours by building a custom test parallelization tool for a 30,000-test suite.
  • Built a hybrid cloud infrastructure combining AWS, VMware ESXi, and Proxmox with OpenVPN, connecting multiple data centers, achieving 100% uptime.
  • Deployed and maintained a Kubernetes cluster hosting blockchain networks. Built an observability stack with Prometheus, Loki, and Grafana.
Technologies: Java, Java 8, Multithreading, Blockchain, REST, Groovy, Python, Ansible, Docker, Kubernetes, Bash, Linux, Code Review, Code Refactoring, Jenkins, Jenkins Job DSL, Microservices, REST APIs, Amazon Web Services (AWS), Apache Tomcat, Distributed Systems, Jetty, Large-scale Distributed Systems, Microservices Architecture, JSON, Hibernate, Software Architecture, Infrastructure as a Service (IaaS), Go, Claude, Codex, Large Language Models (LLMs), AI Prompts, Cloud Infrastructure, Test Automation, Debugging, Apache Kafka, DevOps, SSH, XML, Spring Boot, Spring

Java Software Engineer

2007 - 2019
FitechSource
  • Built the back end for Stanford University's laboratory management system serving 100+ researchers. The system includes real-time inventory tracking, grant management, purchase request workflows, and usage analytics.
  • Developed core features for commercial distributed computing products, including clustering logic, failover mechanisms, testing infrastructure, and production deployment support.
  • Implemented high-performance back-end services for financial trading platforms, including market data processing, order routing, session management, and transaction handling.
  • Created back-end services for stock exchanges, handling real-time trading operations and transaction processing.
  • Developed REST APIs and microservices using Spring framework with PostgreSQL and MySQL databases.
  • Designed distributed systems components, including message routing, multi-node synchronization, fault tolerance, and graceful degradation.
  • Optimized database performance through query tuning, indexing strategies, and connection pool configuration.
  • Built full-stack features using AngularJS, Vue.js, and GWT, including bioinformatics data visualization, real-time dashboards, and inventory management interfaces.
  • Managed PostgreSQL and MySQL production databases, including performance tuning, schema migrations, replication setup, and backup/restore procedures.
Technologies: Java, Java 8, Java SE (Core Java), JDBC, REST, REST APIs, Multithreading, PostgreSQL, MySQL, Linux, Bash, Python, Spring, Spring Boot, Microservices, Code Refactoring, Code Review, Docker, Amazon Web Services (AWS), Apache Tomcat, Distributed Systems, Large-scale Distributed Systems, Microservices Architecture, JSON, Hibernate, Software Architecture, Infrastructure as a Service (IaaS), Go, Cloud Infrastructure, JavaScript, Test Automation, Debugging, Apache Kafka, DevOps, SSH, XML, API Backwards Compatibility

Java Software Engineer

2006 - 2007
ZAO Eureca
  • Developed Java back-end modules for an automated logistics platform managing hospital food supply for Russian Ministry of Defence facilities.
  • Designed and implemented a database layer using JDBC and SQL for supply chain tracking and inventory management.
  • Built reporting and data processing components for automated ordering, delivery scheduling, and stock reconciliation across multiple facilities.
Technologies: Java, Java SE (Core Java), JDBC, SQL, XML, Spring

Experience

Renzu Select, a Professional Photo Culling App

https://apps.apple.com/us/app/renzu-select/id6756066357
Renzu Select is an application built for professional photographers who need to process thousands of RAW files after a shoot. I designed, developed, and shipped this product to the App Store entirely on my own as a solo developer. The app loads embedded JPEG previews from RAW files (.NEF, .RAF, .CR2/CR3, .ARW, .DNG) instantly, so photographers can start culling without waiting for heavy editors to launch.

I implemented an on-device ML pipeline for smart stacking. The app analyzes photos using vector embeddings and visual-similarity clustering to group similar shots automatically. All AI processing runs locally on the Mac with zero cloud dependency. Other features I built include a 5-star rating system with XMP metadata support, dynamic viewing themes, a non-blocking import pipeline with background caching, automatic session recovery, and a professional export system with naming templates and metadata presets. All heavy processing runs in isolated background threads to keep the UI responsive.

Neru Plan, a Smart Meal Planning App for iOS and iPad

https://apps.apple.com/ca/app/neruplan/id6758759028
Neru Plan is a meal planning app for iOS and iPad that I designed, developed, and shipped to the App Store as a solo developer. The name comes from the Japanese verb "neru", which means "to cultivate a plan carefully." The app uses Apple intelligence for on-device AI recipe imports: users can snap a photo of a recipe or paste a link, and the app extracts and structures all ingredients and steps locally. No data ever leaves the device, and the app works entirely offline.

I built a custom ingredient matching system, which I call "Atoms", according to which ingredients aren't stored as plain text. "Tomato" in a soup and "Tomatoes" in a salad automatically merge into one item on the shopping list. The shopping list engine handles automatic aggregation and unit conversion between cups, tablespoons, and metric measurements. Other features include an infinite-scroll calendar with drag-and-drop meal planning, dynamic serving size scaling that recalculates shopping lists without modifying original recipes, and iCloud sync between iPhone and iPad. I also built a recipe import parser supporting 10+ popular cooking websites. All AI processing uses Apple Foundation Models running locally.

Moku View

https://github.com/eeexception/MokuView
Moku View is a native macOS storage analyzer built with Swift and SwiftUI. It visualizes disk space usage through a hierarchical tree and a synchronized pie chart. It is a lightweight, performance-focused alternative to TreeSize, designed for identifying large files and folders.

Skills

Libraries/APIs

REST APIs, JDBC, Jenkins Job DSL

Tools

Ansible, Apache Tomcat, Jetty, Claude, Codex, AI Prompts, IntelliJ IDEA, Slack, Jenkins, Photoshop CC, Adobe Lightroom

Languages

Bash, Java, Java 8, XML, Go, Python, Dart, Groovy, Java SE (Core Java), SQL, Swift, JavaScript

Frameworks

Spring Boot, Spring, Hibernate, Flutter, SwiftUI

Paradigms

Test-driven Development (TDD), KISS, Microservices, Code Refactoring, Test Automation, DevOps, REST, Microservices Architecture

Platforms

Linux, Docker, Amazon Web Services (AWS), Kubernetes, Blockchain, Apache Kafka, MacOS, Visual Studio Code (VS Code), Apple Intelligence, RevenueCat

Storage

PostgreSQL, MySQL, JSON

Other

Multithreading, SOLID Principles, Code Review, Distributed Systems, Large-scale Distributed Systems, Large Language Models (LLMs), Cloud Infrastructure, Debugging, Headshots, Photoshoot Production, Photography, SSH, API Backwards Compatibility, Software Architecture, Infrastructure as a Service (IaaS), AI Model Training, ONNX Runtime, EfficientNet, On-Device AI, App Store Connect, AppStore, Artificial Intelligence (AI), Neural Networks, Machine Learning, Data Science, DSLR Photography, Capture One, Color Grading, Renzu Select, Event photography, Corporate headshots, Fashion photography, Editorial photography, Automotive/motorsports, Portrait & model photography, Sports photography, Agentic Coding

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