
Valerii Konchin
Verified Expert in Engineering
Software Engineer and Developer
Vancouver, BC, Canada
Toptal member since February 11, 2026
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
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)
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.
Software Developer
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.
Founder & Event/Portrait Photographer
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.
Senior Software Engineer
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.
Java Software Engineer
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.
Java Software Engineer
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.
Experience
Renzu Select, a Professional Photo Culling App
https://apps.apple.com/us/app/renzu-select/id6756066357I 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/id6758759028I 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/MokuViewSkills
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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