Yanjun L.

I help teams ship AI features, API integrations, and production web scrapers — primarily in Golang, with Python/FastAPI and React when the stack needs them. Ex-Alibaba software engineer. Top Rated on Upwork. Strongest day-to-day language: Go. Web scraping / data extraction is a core strength alongside API work. I work best on focused builds: high-performance Go services, reliable crawlers at scale, add an LLM/RAG workflow to an existing app, wire a third-party API, or migrate a payment/CRM flow — not vague “build me an AI SaaS from scratch” briefs. What I typically deliver • Golang services & APIs — concurrent, production-ready backends, workers, and integrations that stay fast under load • Web scraping & data pipelines — site crawlers, anti-bot-aware extraction, structured datasets, scheduled jobs, and scrapers that feed your DB/API (Python or Go) • AI & API integration — OpenAI / Claude into your product: structured extraction, agents, RAG; FastAPI or Go services that React can call cleanly • System integration & migration — Stripe, HubSpot, Salesforce, custom CRMs; checkout/payment flows; syncing data between tools without breaking what’s already live • Stabilization — legacy rescue, debugging undocumented services, Chrome extensions and small automation where ops need a sharp tool Stack I use day to day Golang · Python · React · FastAPI · Laravel · PHP · Vue.js · Node.js · MySQL · OpenAI / Claude · AWS · Linux / CI-CD · Chrome Extension How I work • Scope first: clear deliverables, realistic timeline, what is in/out • Prefer extending your existing repo over rewriting everything • Secure defaults for API keys, webhooks, and client data; NDAs welcome • Respect robots/ToS and target site constraints — I flag legal/risk issues early • Direct updates in plain English — Asia timezone (UTC+8), overlap available for US/EU kickoffs Good fit if you need: “Golang API / microservice”, “web scraper / crawler that doesn’t break weekly”, “add AI to this React app”, “FastAPI or Go service for our LLM flow”, “Stripe/HubSpot integration or migration”, or “fix / harden this API”. Send the repo link or a short brief — I’ll tell you quickly whether I’m the right person and what the first milestone should be.