# Serverless P2P NFT Marketplace on Polygon — Powered by GenosDB

> *Most dapps hammer an RPC and shove a wallet extension in your face. I took the on-chain marketplace from OVGrid and rebuilt it as a ~1,600-line example where the database is the read layer — and your identity is your wallet.*

Open two browser tabs at [**dMarket**](https://estebanrfp.github.io/dMarket/). Browse the marketplace in both — no wallet, no sign-up, no spinner waiting on an RPC. The items are just *there*, and a change in one tab shows up in the other. That isn't a backend doing the work. It's a peer-to-peer graph database.

dMarket is a small, faithful slice of the marketplace that runs inside [OVGrid](https://github.com/estebanrfp/ovgrid) — the WebGPU planet I [wrote about here](https://genosdb.com/a-live-webgpu-planet-with-no-backend-powered-by-genosdb). I pulled the blockchain layer out, trimmed it to ~1,600 readable lines of vanilla JavaScript with no build step, and kept it pointed at the *same real contracts* OVGrid uses on Polygon. It exists so you can copy a pattern that actually works instead of reinventing it.

## The problem with most blockchain front-ends

Every wallet, every render, every visitor hits the same RPC for the same data. There's no real-time sync between users unless you stand up an indexer and a websocket server — a backend, the very thing crypto was supposed to get rid of. And before anyone can even *look*, you make them install MetaMask.

I wanted to show a different shape.

## First, what GenosDB is

[GenosDB](https://github.com/estebanrfp/gdb) is a peer-to-peer graph database that runs entirely in the browser. No central server: data lives locally (OPFS), replicates between peers over WebRTC, and every operation is signed by your own key. You read it reactively with `db.map(query, cb)`. (More in the [examples](https://github.com/estebanrfp/gdb/blob/main/docs/genosdb-examples.md).)

## The key idea: the chain is the truth, GenosDB is the mirror

Polygon stays the source of truth for ownership — money is money. But you don't read *from* the chain on every render. You read it once, write the result into GenosDB, and from then on everyone reads the database:

```js
// Read the chain (authoritative) once, mirror it into GenosDB:
const listings = await chain.getActiveListings()        // 2 Multicall3 calls
await Promise.all(listings.map(l =>
  db.put({ type: 'listing', ...l }, `listing_${l.listingId}`)
))

// Everywhere else, read reactively — never the RPC again:
db.map(({ id, value, action }) => repaint())            // the ONE reactive read
```

After a buy or a listing confirms on-chain, the same thing happens: `db.put` the new state, and `db.map` streams it to every connected peer. The read layer never changes whether an item was just discovered on-chain or just created by someone two seconds ago. The database *is* the abstraction — fast, offline-capable, peer-to-peer, with no indexer in the middle.

## The part I'm proudest of: your identity is your wallet

GenosDB's Security Manager already gives every user a cryptographic identity — an address and a private key derived from a recovery phrase. Here's the thing nobody points out: **that's an Ethereum account.** The same key that signs your peer-to-peer database operations signs your Polygon transactions.

```js
// A GenosDB login hands you a usable wallet. One key, two worlds.
const id = await db.sm.loginOrRecoverUserWithMnemonic(phrase) // { address, privateKey }
const wallet = new ethers.Wallet(id.privateKey, provider)     // signs on-chain txs
// wallet.address === db.sm.getActiveEthAddress()   ✓  no MetaMask
```

No extension, no second wallet, no bridging. You log in once and you can both sync P2P and transact on-chain with the exact same identity. dMarket even asserts the two match before it ever signs. See the [Security Manager docs](https://github.com/estebanrfp/gdb/blob/main/docs/sm-api-reference.md).

## What GenosDB actually buys you here

| What a marketplace needs | How dMarket does it with GenosDB |
| --- | --- |
| Live updates between users | `db.map()` over WebRTC — no indexer, no websocket backend |
| Browse instantly, even offline | local-first reads from GenosDB (OPFS) |
| A wallet | the GenosDB identity *is* the wallet — no MetaMask |
| "Who owns what" | mirrored P2P, re-derivable from the chain anytime |

## Simplified, but real

dMarket is deliberately a *reference example*, not the full product. It does mint, list, buy and offer — and stops there. No auctions, bundles, rentals, royalties, analytics or a 3-D world; that breadth lives in OVGrid. But what's here is the real, battle-tested integration: real ABIs, real contracts on Polygon Amoy, the real identity bridge. Read dMarket to learn the pattern; study [OVGrid](https://github.com/estebanrfp/ovgrid) to see it at full scale.

Browsing works for anyone with no wallet — that's the GenosDB showcase. To actually transact you connect an identity and grab free test POL from the [Amoy faucet](https://faucet.polygon.technology/); the README is honest about the prerequisites.

## Try it / read it

*   ▶ **Play it live** — [estebanrfp.github.io/dMarket](https://estebanrfp.github.io/dMarket/) (open two tabs)
    
*   💻 **Read the code** — [github.com/estebanrfp/dMarket](https://github.com/estebanrfp/dMarket) (~1,600 lines, no build)
    
*   🌍 **The full world it came from** — [OVGrid](https://github.com/estebanrfp/ovgrid)
    
*   🗄️ **The database** — [GenosDB](https://github.com/estebanrfp/gdb) · [reactive reads](https://github.com/estebanrfp/gdb/blob/main/docs/map-guide.md) · [identity & security](https://github.com/estebanrfp/gdb/blob/main/docs/sm-api-reference.md)
    

## Why this matters

We keep rebuilding the same backend — an indexer here, a websocket there, a wallet popup in front — to do things a peer-to-peer database can just *do*. dMarket is a small proof that you can put a real blockchain behind a real-time, offline-capable, serverless front end, and have the whole thing be readable in an afternoon.

The chain is the truth. The database is the mirror. Your identity is your wallet. No backend.

* * *