stripemeter

# StripeMeter

StripeMeter is a Stripe-native usage metering system that ensures correct usage totals for usage-based billing. It dedupes retries, handles late events with watermarks, keeps running counters, and pushes only deltas to Stripe.

## Quick Start

```bash
git clone https://github.com/geminimir/stripemeter && cd stripemeter
cp .env.example .env && docker compose up -d && pnpm -r build
pnpm db:migrate && pnpm dev
```

## Core Concepts

### Events (Immutable Ledger)
Every usage event stored with deterministic idempotency key. Events are never deleted or modified.

### Counters (Materialized Aggregations)
Pre-computed aggregations (sum/max/last) by tenant, metric, customer, and period. Updated in near-real-time.

### Watermarks (Late Event Handling)
Each counter maintains a watermark timestamp. Events within lateness window (default 48h) trigger re-aggregation.

### Delta Push (Stripe Synchronization)
Tracks `pushed_total` per subscription item and only sends delta to Stripe.

## API Endpoints

### Ingest Events

```bash
curl -X POST http://localhost:3000/v1/events/ingest \
  -H "Content-Type: application/json" \
  -d '{
    "events": [{
      "tenantId": "your-tenant-id",
      "metric": "api_calls",
      "customerRef": "cus_ABC123",
      "quantity": 100,
      "ts": "2025-01-16T14:30:00Z"
    }]
  }'
```

### Get Cost Projection

```bash
curl -X POST http://localhost:3000/v1/usage/projection \
  -H "Content-Type: application/json" \
  -d '{"tenantId": "your-tenant-id", "customerRef": "cus_ABC123"}'
```

### Health & Metrics

- Readiness: `GET /health/ready`
- Metrics: `GET /metrics`
- Events: `GET /v1/events?tenantId=X&limit=10`

## Node.js SDK

```typescript
import { createClient } from '@stripemeter/sdk-node';

const client = createClient({
  apiUrl: 'http://localhost:3000',
  tenantId: 'your-tenant-id',
  customerId: 'cus_ABC123'
});

// Track usage
await client.track({
  metric: 'api_calls',
  customerRef: 'cus_ABC123',
  quantity: 100,
  meta: { endp...