I specialize in reverse-engineering web targets, taking apart protected private APIs, and building high-throughput scrapers that don't get banned:

• Bypassing anti-bot protections without bloated browsers: Wherever possible, I avoid running heavy headless Chrome instances. In depop-tls-scraper, I spoof TLS fingerprints (JA3/JA4) and HTTP/2 frames directly in Go (bogdanfinn/tls-client) to bypass Cloudflare at raw HTTP wire speeds (~20 MB RAM instead of hundreds of megabytes per browser).
• Cryptographic auth & private API reverse engineering: Rather than scraping raw HTML, I inspect mobile apps and frontend bundles to find private REST/GraphQL gateways. In unifeed-marketplace-core, I reverse-engineered Mercari Japan's DPoP authentication by generating ephemeral ECDSA P-256 key pairs and signing ES256 JWT tokens on Go. In xianyu-mtop-scraper, I implemented Alibaba's MTOP MD5 HMAC request signing with automatic Playwright session self-healing.
• Stealth browser automation: When a target strictly requires a real browser environment, I use Camoufox (anti-detect Firefox C++ fork) with Playwright to beat advanced browser fingerprinting, CDP leak detection, and behavioral heuristics (x-stealth-automation).
• Adversarial computer vision & anti-crawling defense: In lens-cloak, I built an adversarial perturbation pipeline that injects high-frequency noise and micro-geometric warping into images, disrupting CNN and Vision Transformer embeddings (Google Lens, PimEyes) while completely sanitizing digital footprints (EXIF/GPS/ICC).
• High-concurrency systems & streaming: Writing clean concurrent worker pools, managing low-level memory/file ring buffers (go-mac-shadowplay), proxy rotation, handling 429 rate-limits, and persisting clean data to SQLite/PostgreSQL.

• depop-tls-scraper — Fast Go scraper using JA3/JA4 TLS spoofing to bypass Cloudflare without launching a browser. Thread-safe deduplication cache and CI test suite.
• unifeed-marketplace-core — High-concurrency Go aggregator for East Asian resale markets featuring Mercari JP ephemeral ECDSA P-256 / ES256 DPoP signing, Yahoo Auctions DOM parsing, and Bunjang API ingestion.
• xianyu-mtop-scraper — Reverse-engineered Alibaba Xianyu (Goofish) MTOP API with client-side MD5 signing, dynamic proxy rotation, and Playwright session self-healing.
• x-stealth-automation — Stealth automation agent built on Camoufox (C++ modified Firefox) and Playwright for bypassing bot detection heuristics.
• lens-cloak — Adversarial perturbation & metadata sanitization engine evading AI visual search crawlers (Google Lens, PimEyes) with Python CLI & Web Canvas Studio.
• go-mac-shadowplay — ShadowPlay-style instant replay and screen recorder for macOS written in Go with ScreenCaptureKit, AVFoundation H.264 ring buffers, and Objective-C bridge.
• etsy-api-pipeline — Concurrent listing pipeline in Go with worker pools, OAuth2 PKCE flow, filtering, and database storage.
• polymarket-intelligence — Prediction market data crawler with cursor pagination, rate-limiting, and exponential backoff.

• Languages: Go, Python, SQL, Bash, Objective-C / C (CGO)
• Scraping & Stealth: Playwright, Camoufox, bogdanfinn/tls-client (JA3/JA4), Headless Chrome/Firefox
• Security & Cryptography: ECDSA P-256, ES256 JWT / DPoP, MD5 HMAC, Adversarial Perturbation
• Network & Proxies: HTTP/2, SOCKS5, Residential/Mobile proxy rotation, rate-limit backoff
• Storage & DevOps: SQLite, PostgreSQL, Docker, Docker Compose, Git, GitHub Actions

• Email: guidiclub@gmail.com
• LinkedIn: linkedin.com/in/valentyn-hrodiuk-85025a447
• GitHub: github.com/guidiguidi
• Status: Open to Warsaw Hybrid (ready to relocate) or Remote B2B opportunities.