THROW Watcher

Node.js/Express service that watches the Tempo chain for ERC-20 Transfer events and sends Web Push notifications to registered THROW wallets.

Setup

1. Generate VAPID keys (once)

npx web-push generate-vapid-keys

Store the output as Railway env vars: VAPID_PUBLIC_KEY, VAPID_PRIVATE_KEY

2. Deploy to Railway

• Create a new service in your Railway project
• Connect this repo (or the throw-watcher/ directory)
• Set environment variables from .env.example
• Railway auto-detects Node.js via package.json

3. Point the THROW PWA at the watcher

In app.js, set:

const WATCHER_URL = 'https://your-railway-service.up.railway.app';

Endpoints

Method	Path	Description
GET	/health	Health check
GET	/throw-watcher/vapid-public-key	Returns VAPID public key for PWA subscription
POST	/throw-watcher/register	Register wallet + push subscription
GET	/throw-watcher/status	Live stats for swarm dashboard
GET	/throw-watcher/throws	Throw history (last 100)
POST	/throw-watcher/test-push	Send test push to a registered address

Architecture

One instance handles ~100K registered wallets. Polls Tempo eth_getLogs every 10s for Transfer events on USDC.e + pathUSD. Bottleneck is Chainstack RPC tier — not the Node.js process.