GammaSkins: Skin Marketplace Platform

What it is

GammaSkins is a marketplace for Counter-Strike skins. Users list items from their Steam inventory, buyers pay by card through Stripe, and bots deliver the items instantly. The whole product depends on one thing: the trade between a buyer and a bot has to complete correctly, every time.

How it’s built

The frontend is Angular (standalone components and signals) with server-side rendering through @angular/ssr, so item pages can be indexed. The backend is Node.js and Express on PostgreSQL, with Stripe as the payment rail. Fulfilment is driven by webhooks, so money, inventory and trade state stay consistent even when requests arrive out of order.

Inventory sync uses Steam’s public inventory endpoints, cross-checked against the items the bots own. Listing, pricing and purchase flows sit on top of the same trade engine patterns that later went into IO Saga.

What it taught me

No other build taught me as much about failure. Two buyers clicking on the same item at once and causing a double-spend race. Webhook retries that have to be idempotent. A trade that is technically “in progress” for up to 30 seconds, and what that does to the UX. Every current lab build is designed with those lessons in mind.