How I Built a Multi-Product AI API Business on Railway — FastAPI + Stripe + x402 + MCP in One Stack

A few months ago I wanted to sell access to AI tools I'd built — a passive income analyzer, an AI strategy consultant, an autonomous commerce layer. The standard approach is: pick a SaaS platform, pay their cut, accept their limitations. Instead I built ACE — an AI commerce engine that handles everything itself. It's been running on Railway for months, delivering license keys, processing Stripe webhooks, and accepting x402 micropayments. Here's the architecture. What ACE does ACE...