Senior Backend Engineer specializing in Go and Python, with hands-on experience building payment systems, from card payments and subscription billing to on-chain stablecoin payments.
I’ve led the development and launch of multiple blockchain services, covering backend engineering and mainnet integration.
15+ years of software engineering experience, 8 years with Go, and 6 years working remotely with teams across the US, Sweden, Israel, and China. Upwork Top Rated Plus.
CORE EXPERTISE
• Payments — Stripe, PayPal, Authorize.Net, Heartland, Pelecard, and USDC payments on Base (L2). Payment processing, subscriptions, billing, tax, and webhooks.
• Backend Engineering — Go, Python, Node.js, gRPC, microservices, Kubernetes, AWS, GCP Cloud Run, Pub/Sub, Docker, Redis, MySQL, Cloud Spanner, and ClickHouse.
• Blockchain — Ethereum, Base, Solidity, Web3.js, Hyperledger Fabric, and Cosmos SDK. Smart contracts, token swap backends, and mainnet integration.
SELECTED ENGINEERING WORK
• Took over a non-operational Node.js/EVM service, resolved integration issues, and implemented USDC payment flows on Base, bringing the service to production launch readiness.
• Migrated a monolithic Go server to microservices on a 40+ service platform, developed shared libraries for authentication, logging, and CDN, and worked on payment, subscription, billing, and tax services integrated with Stripe and PayPal.
• Built a parking citation payment system integrating Authorize.Net and Heartland.
• Led the development and launch of a blockchain-based credit data service on Ethereum and Hyperledger Fabric, covering backend design and development, deployment, and AWS operations.
• Led the development of Cosmos SDK-based blockchain services for a digital asset management company, including Cosmos Hub integration, a cross-chain token bridge, and mainnet launch.
• Rebuilt a FastAPI service for a decentralized GPU network that allocates miner machines to clients and returns SSH access, with health checks and webhooks.
• Built a live-stream chat push service in Go, fanning room messages out to viewers via Redis Pub/Sub and Server-Sent Events (SSE).
• Maintained Go microservices for event registration, payments (Pelecard), and Keycloak-based user profiles; built a lecture subtitles service and Python automation for Zoom recordings.
If you need an engineer to build or scale payment systems — traditional or on-chain — or develop reliable backend and blockchain services, let’s talk.
Experience: 8 years
Yearly salary: $86,000
Hourly rate: $40
Nationality: 🇰🇷 South Korea
Residency: 🇰🇷 South Korea
Experience
backend developer
gettr 2025 - 2025
• Built a real-time chat system in Go, using Redis Pub/Sub for message fan-out and SSE for streaming messages to clients. • Implemented connection lifecycle management and message delivery handling for long-lived client sessions.
backend developer
Neural Internet 2025 - 2025
• Rebuilt a FastAPI-based resource allocation API for a Bittensor GPU compute subnet, enabling clients to allocate, manage, and monitor GPU resources from network miners. • Implemented spec-based miner matching, allocation and deallocation flows, and decryption of RSA-encrypted SSH credentials returned by miners. • Built background health checks with auto-deallocation and ONLINE/OFFLINE webhooks with retry, secured by mTLS.
blockchain developer
wildfireart 2025 - 2025
• Took over a non-operational blockchain service and resolved critical issues across the Node.js and EVM stack, including Ethereum, Base, and USDC transaction integrations. • Fixed critical bugs in Solidity smart contracts and refactored and optimized them, reducing gas costs and bringing contract size under the EIP-170 (24KB) deployment limit. • Maintained the frontend’s Web3.js integration to keep it in sync with backend and smart contract changes. • Redesigned the system architecture to align with the original product requirements and completed preparations for mainnet launch.
backend / blockchain developer
INOVBE INC 2024 - 2024
• Led the development of a Go-based token trading application on the Xelis blockchain, implementing token exchange flows. • Built backend services for wallet management and transaction processing, integrated the Xelis SDK, and deployed services with Docker.
backend developer
E-commerce startup 2024 - 2026
• Migrated a monolithic Go server to microservices on GCP, developing and maintaining shared libraries for auth, logging, and CDN (Spanner, MySQL, Pub/Sub, Cloud Run). • Developed and maintained payment, subscription, billing, and tax services integrated with Stripe, PayPal, and other gateways. • Maintained and extended a custom Liquid rendering engine in Go and a Fastly-based page delivery architecture. • Built ClickHouse analytics APIs and Spanner-to-MySQL migration tooling. • Resolved security findings and distributed authentication race conditions.
backend developer
FullThrottle 2023 - 2023
• Developed a Go-based YouTube video management server with gRPC APIs. • Implemented backend workflows for video ingestion and metadata management. • Optimized video processing through parallel uploads and batch processing.
backend developer
Park Loyalty Inc 2022 - 2022
• Developed a FastAPI backend system for parking citation payments, integrating Authorize.net and Heartland payment gateways. • Implemented payment transaction workflows, error handling, and reporting.
backend developer
Bnei Baruch 2022 - 2024
• Maintained Go microservices for event and broadcast registration, orders and payments (Pelecard), and user profiles synced with Keycloak. • Built a lecture subtitles and slides service in Go with Keycloak OIDC authentication and document ingestion from a media archive. • Built Python automation that bulk-downloads Zoom recordings across account users via Server-to-Server OAuth. • Deployed services with Docker and GitLab CI, with automated staging and manual production releases. • Developed the initial frontend, implementing core pages and user flows.
backend / blockchain developer
vegax 2021 - 2022
• Led the Konstellation (DARC) Cosmos SDK chain from mid-development to mainnet launch, including mainnet genesis and network configuration. • Built custom Cosmos SDK modules for an exchange-rate oracle and token issuance, and upgraded the chain’s Cosmos SDK with IBC and CosmWasm support, including IBC connection to Cosmos Hub. • Built a DARC↔BNB Smart Chain token bridge in Go (API, block parser, and worker services) with an order state machine, expiry handling, and automatic retries. • Operated validator and full nodes for the network. • Maintained the oracle price feeder, an explorer REST API with Redis caching, and network tooling for localnet, testnet, and mainnet deployment.
backend developer
Clean.Tech 2020 - 2021
• Maintained and optimized Go and Python microservices for a solar installation company's operations management system, including customer and inventory management. • Developed a Telegram chatbot to automate customer interactions. • Managed deployment, scaling, and monitoring of production services on GCP.
backend developer
Yonego 2017 - 2017
• Migrated a monolithic PHP server to Go microservices. • Containerized and deployed the Go microservices on Kubernetes. • Implemented a Backend for Frontend (BFF) layer in Go to aggregate microservice APIs for client applications.
backend / blockchain developer
MyCreditChain 2017 - 2020
• Led the development and launch of a blockchain-based credit data service on Ethereum and Hyperledger Fabric. • Led ICO preparation and developed smart contracts for the entire lifecycle, from token sales to service launch, including token management. • Managed AWS infrastructure and Kubernetes clusters for backend services and blockchain nodes, including provisioning, scaling, and monitoring.
backend developer
Anx International 2016 - 2016
Implemented internationalization (i18n) for a Bitcoin debit card service’s localization server, including database migrations to support multilingual content.
backend developer
Chaatz 2015 - 2016
• Ported the messaging app’s backend services to Go, building client-facing APIs for proxy number provisioning and customer management, and integrating with an Elixir-based message delivery server. • Built an internal ERP platform to support business operations.
full stack developer
lionbridge 2014 - 2014
• Developed Go tools to automate translation preparation workflows. • Built CMS and localization management systems for translation projects.
full stack developer
Computer Architechs International Corporation 2012 - 2013
• Maintained annual iOS and Android conference agenda apps for an IBM event. • Maintained Firestone Complete Auto Care (Bridgestone) vehicle service apps for iOS and Android, including an iPad port. • Developed the American Academy of Orthopaedic Surgeons (AAOS) Musculoskeletal Exam – Spine app for iOS and Android.
full stack developer
KT capital 2010 - 2011
Developed an in-house ERP application covering internal business operations, including accounting and credit management.
Skills
aws
blockchain-engineer
cosmos
couchbase
docker
ethereum
gcp
hyperledger-fabric
kubernetes
mongo
python
golang