> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ondb.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Cost Estimation

> Understanding operation costs in OnDB

OnDB uses the x402 payment protocol for cost handling. When a write or read operation requires payment, the server returns a 402 response with a payment quote. The SDK handles this automatically via the payment callback.

## How Pricing Works

Costs are determined server-side based on:

| Factor               | Description                                      |
| -------------------- | ------------------------------------------------ |
| **Data size**        | Amount of data being stored (KB)                 |
| **Indexed fields**   | Number and type of indexes on the collection     |
| **Price indexes**    | Value-based pricing via write/read price indexes |
| **Creator premiums** | Revenue sharing with content creators            |

## Inspecting Costs via Payment Callback

The payment callback receives an `X402Quote` with full cost details:

```typescript theme={null}
const result = await client.store(
  { collection: 'users', data: [{ name: 'Alice' }] },
  async (quote) => {
    // Inspect the cost before paying
    console.log('Total cost:', quote.totalCost, quote.tokenSymbol);
    console.log('Amount (raw):', quote.amountRaw);
    console.log('Pay to:', quote.brokerAddress);
    console.log('Network:', quote.network);
    console.log('Chain:', quote.chainType);
    console.log('Expires:', new Date(quote.expiresAt * 1000));

    // Process payment
    const txHash = await processPayment(quote);
    return { txHash, network: quote.network, sender: walletAddress, chainType: quote.chainType, paymentMethod: 'native' };
  },
  true
);
```

## Estimating Batch Costs

For batch operations, the payment callback is invoked once for the entire batch. The quote reflects the total cost:

```typescript theme={null}
const records = generateRecords(1000);

const result = await client.store(
  { collection: 'batch_data', data: records },
  async (quote) => {
    console.log(`Batch of ${records.length} records:`);
    console.log(`  Total cost: ${quote.totalCost} ${quote.tokenSymbol}`);
    console.log(`  Per record: ~${(quote.totalCost / records.length).toFixed(6)} ${quote.tokenSymbol}`);

    const txHash = await processPayment(quote);
    return { txHash, network: quote.network, sender: walletAddress, chainType: quote.chainType, paymentMethod: 'native' };
  },
  true
);
```

## Retention Costs

Use `getRetentionCost()` to estimate ongoing storage costs for your collections:

```typescript theme={null}
const costs = await client.getRetentionCost();

console.log('Total monthly cost:', costs.total_monthly_cost, 'USDC');
console.log('Projected next month:', costs.projected_next_month_cost, 'USDC');

for (const col of costs.collections) {
  console.log(`  ${col.collection}: ${col.monthly_cost} USDC/month (${col.size_kb} KB)`);
}
```

## Next Steps

<CardGroup cols={2}>
  <Card title="Write Payments" icon="credit-card" href="/payments/write-payments">
    Execute payments
  </Card>

  <Card title="PriceIndex" icon="tags" href="/payments/price-index">
    Value-based pricing
  </Card>
</CardGroup>