Mykhailo Yuriyovych S.

Senior back-end developer with 20+ years of experience in PHP, Node.js/TypeScript and Python, plus the servers they run on. I build APIs, payment flows, crypto and Web3 back ends, WordPress/WooCommerce plugins and data pipelines, and I deploy and secure them myself. I have worked with blockchains since 2017, when I ran Bitcoin, Ethereum and Litecoin full nodes for a crypto exchange. WHAT I DO - Back ends and APIs: REST APIs designed API-first, background workers, queues, webhooks with signatures and retries, multi-process services in PHP 8, Node.js/TypeScript and Python. - Web3 and crypto: Solidity contracts with Foundry tests, EVM chain watchers with reorg handling, relayers, Sign-In with Ethereum, MetaMask and WalletConnect, exchange APIs (Bybit), on-chain trading bots. - WordPress and WooCommerce: custom plugins and payment gateways, member pricing and access rules, third-party integrations, performance work (mobile PageSpeed from 66 to 93), plugin security audits. - Servers, DevOps and security: Linux (Debian/Ubuntu), NGINX, OpenLiteSpeed, Docker, systemd, Cloudflare (WAF, origin lockdown, tunnels), GitHub Actions CI/CD, backups, monitoring, server migrations, malware and backdoor cleanup, hardening. - Scraping and data: proxy-rotated scrapers, queue-based pipelines, high-volume imports into production databases. SELECTED WORK - Stablevoy, my own non-custodial USDC/USDT payment gateway, live on six EVM networks. Solidity contracts (CREATE2 deposit addresses, on-chain fee split, no owner key, 100% test coverage, verified source), Node.js/TypeScript services (API, chain watcher, sweeper, webhook dispatcher), Next.js dashboard and a WooCommerce plugin. - On-chain trading bot on BNB Chain in TypeScript and ethers v6: reacts within seconds, races several RPC providers, sends through a private route, has a replay backtest harness. - Trading signals platform with Bybit auto-trading (orders, multiple take-profits, PnL), crypto payments, Telegram and web push notifications, a Flutter Android app, and an open-source Bybit PHP library on Packagist. - Amazon/Walmart product parser that processed over 1M listings a day for a year and a half; a newer Amazon UPC pipeline crawled 18M+ ASINs with a proxy pool and a MySQL queue. - Security cleanup of WordPress fleets: a 170-site server audited (170 databases, 256 admin accounts), backdoors removed, including an attacker account restored by MySQL triggers; servers hardened and tuned. - Video widget SaaS: Stripe subscription billing, direct browser uploads to Bunny Stream over TUS, a plugin API for WordPress and Shopify, multi-tenant agency accounts. - Server migrations, including a 219 GB production database moved to a new server behind a Cloudflare-only firewall. - Mobile reverse engineering: rooted Android, my own LSPosed module and a Play Integrity solution; Instagram private API integration. STACK - Languages: PHP 8, TypeScript/JavaScript (Node.js), Python, Solidity, SQL, Bash, Dart (Flutter). - Back end: Fastify, vanilla PHP with SOLID structure, WordPress/WooCommerce. - Front end: Next.js, React, Vue 3, Bootstrap. - Databases: MySQL/MariaDB, PostgreSQL, MongoDB, Redis. - Infra: Hetzner, DigitalOcean, Docker, NGINX, Cloudflare, RabbitMQ, Memcached, GitHub Actions. - Web3: Foundry, ethers v6, WalletConnect, SIWE. - Payments and APIs: Stripe, Paddle, PayPal, NOWPayments, Bybit, Meta Graph API, Twilio, Webflow CMS, HubSpot, Telegram. - Testing: PHPUnit, Vitest, Playwright, Foundry fuzz and invariant tests. HOW I WORK - A short written spec before code for anything non-trivial, so scope and cost are agreed up front. - Clean, tested code with SOLID structure; I read unfamiliar codebases quickly and fit into existing patterns. - Backups before any risky change, and no silent workarounds: problems surface where you can see them. - Clear written updates. Open to long-term contracts.