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William Balance
FR EN KO

Tech stack

The tools I actually use every day to ship web apps and AI systems to production. Not a padded resume list: only what I work with regularly, with a short note on real usage.

01

Languages

  • TypeScript
    Primary language for web, Node back-ends and agents.
  • Python
    AI scripts, data pipelines, quick prototyping with LangChain and LlamaIndex.
  • JavaScript
    When TypeScript is not available, or for one-off scripts.
  • SQL
    Postgres daily, complex queries and index tuning.
  • HTML / CSS
    Clean base, Tailwind for composition, accessibility taken seriously.
02

Web frameworks

  • Next.js
    My default pick for full-stack apps with the App Router.
  • Astro
    Ultra-fast multilingual content sites, SEO-first.
  • React
    Reusable components, hooks, proven state patterns.
  • Hono
    Lightweight APIs on Cloudflare Workers, low global latency.
  • Express
    Classic Node back-ends when the ecosystem calls for it.
03

AI and LLMs

  • Anthropic Claude API
    Claude API integration for agents, long-context reasoning, tool use.
  • OpenAI API
    GPT-4 / GPT-4o for generation, embeddings and function calling.
  • LangChain
    Chain orchestration when the complexity actually justifies it.
  • LlamaIndex
    Structured RAG on heterogeneous sources, advanced indexing.
  • Embeddings
    text-embedding-3, Voyage, Cohere depending on use case.
  • RAG
    Retrieval-augmented pipelines, thoughtful chunking, reranking.
  • Vector DBs: Pinecone, pgvector, Qdrant
    pgvector for simplicity, Qdrant for performance, Pinecone when you want it managed.
04

AI agents

  • Claude Agent SDK
    Autonomous agents with native tool use and context management.
  • Multi-agent orchestration
    Planner-executor patterns, specialized sub-agents, supervision.
  • Tool use
    Exposing internal and external APIs as typed tools.
  • MCP (Model Context Protocol)
    MCP servers to connect Claude to structured data sources.
05

Databases

  • PostgreSQL
    Default database, with pgvector and jsonb extensions.
  • SQLite
    Edge-friendly via D1, great for light local apps.
  • Redis
    Cache, rate limiting, queues, pub/sub.
  • MongoDB
    When the document model is actually a better fit.
06

Infrastructure

  • Cloudflare
    Pages, Workers, R2, D1: global edge, predictable pricing.
  • Vercel
    Fast Next.js deploys when I want zero config.
  • Docker
    Reproducible environments, self-hosted services.
  • GitHub Actions
    CI/CD, tests, linting, automated deploys.
07

Observability

  • Sentry
    Production errors, traces, alerting.
  • PostHog
    Product analytics and feature flags.
  • Structured logs
    JSON logs, request-id correlation, readable dashboards.
08

Dev tooling

  • Claude Code
    Main agent for coding, refactoring and navigating projects.
  • Cursor
    Secondary editor when I need a classic IDE with AI built in.
  • Git
    Short branches, atomic commits, reviews taken seriously.
  • Linear
    Minimal project management, focused on execution.

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