What we've learned shipping Meridian — an MCP server with real auth, Stripe billing, RAG via Vectorize, and SSE streaming on Cloudflare's free tier. Plus side notes on photonic / quantum retrieval research.
Most MCP tutorials show npx create-mcp and a Hello-world tool. Real servers in production need auth, per-key quotas, billing, and an upgrade path. Here's the architecture we use for ask-meridian.uk — entirely on Cloudflare's free tier — and the specific gotchas you'll hit.
Most RAG systems either retrieve from a static corpus or end-to-end LLM-rank. Meridian does neither. Llama-3.3-70B authors fresh skills per task; a deterministic JS classifier assigns each one a celestial class (planet/moon/trojan/asteroid/comet/irregular) based on physics-style features. Why the metaphor, why the deterministic step, and where it goes next.
Workers AI for embeddings (free tier), Vectorize for semantic search (free tier), AI Gateway for caching + observability (free). The whole stack costs $0 until you cross 100k requests/month. Here's the wiring we use for meridian's RAG layer.