# Block intervals \[Run logic on a regular schedule]

To run indexing logic on a **regular schedule**, use the `blocks` field in `ponder.config.ts`. Block intervals are useful for aggregations, time-series logic, and bulk updates using raw SQL.

This guide describes each configuration option and suggests patterns for common use cases. Visit the config [API reference](/docs/api-reference/ponder/config) for more information.

## Example

This config instructs the indexing engine to run an indexing function every 10 blocks starting at the start block – `1000`, `1010`, `1020`, and so on.

```ts [ponder.config.ts]
import { createConfig } from "ponder";

export default createConfig({
  chains: {
    mainnet: { id: 1, rpc: process.env.PONDER_RPC_URL_1 },
  },
  blocks: {
    ChainlinkOracleUpdate: {
      chain: "mainnet",
      interval: 10, // Every 10 blocks
      startBlock: 1000,
    },
  },
});
```

Now, we can register an indexing function for the `ChainlinkOracleUpdate:block` event. This example reads the latest price from the Chainlink oracle contract and inserts a row into the `priceTimeline` table.

```ts [src/index.ts]
import { ponder } from "ponder:registry";
import { priceTimeline } from "ponder:schema";
import { ChainlinkOracleAbi } from "../abis/ChainlinkOracle.ts";

ponder.on("ChainlinkOracleUpdate:block", async ({ event, context }) => {
  // Fetch the price at the current block height (1000, 1010, 1020, etc.)
  const latestPrice = await context.client.readContract({
    abi: ChainlinkOracleAbi,
    address: "0xD10aBbC76679a20055E167BB80A24ac851b37056",
    functionName: "latestAnswer",
  });

  // Insert a row into the price timeline table
  await context.db.insert(priceTimeline).values({
    id: event.id,
    timestamp: event.block.timestamp,
    price: latestPrice,
  });
});
```

## Name

Every block interval must have a name, provided as a key to the `blocks` object. The name must be unique across `blocks`, `contracts`, and `accounts`.

Use a descriptive name to indicate the purpose of the block interval.

```ts [ponder.config.ts]
import { createConfig } from "ponder";

export default createConfig({
  chains: { /* ... */ },
  blocks: {
    ChainlinkOracleUpdate: { // [!code focus]
      chain: "mainnet",
      interval: 10,
      startBlock: 19783636,
    },
  },
});
```

## Interval

Use the `interval` option to specify how often the indexing function should run. A block interval with a start block of `100` and an interval of `10` will index blocks `100`, `110`, `120`, `130`, and so on.

### Block time

It's often easier to think about a *time* interval instead of a *block* interval. To convert between the two, divide the time interval by the chain's average block time.

For example, if the block time is 3 seconds and you want to run an indexing function once per day:

```ts
// 24 hours per day, 60 minutes per hour, 60 seconds per minute
const secondsInterval = 24 * 60 * 60;
// 3 seconds per block
const blockTime = 3;
// 28800 blocks per day
const blockInterval = secondsInterval / blockTime;
```

To find the block time of a specific chain, check the chain's documentation website or block explorer. Most Etherscan deployments have a [`/chart/blocktime`](https://polygonscan.com/chart/blocktime) page.

## Chain

The `chain` option for block intervals works the same way as it does for contracts. You can specify a different `interval`, `startBlock` and `endBlock` for each chain.

```ts [ponder.config.ts]
import { createConfig } from "ponder";

export default createConfig({
  chains: { /* ... */ },
  blocks: {
    PointsAggregation: {
      chain: {
        mainnet: {
          startBlock: 19783636, // [!code focus]
          interval: (60 * 60) / 12, // Every 60 minutes (12s block time) // [!code focus]
        }, 
        optimism: { 
          startBlock: 119534316, // [!code focus]
          interval: (60 * 60) / 2, // Every 60 minutes (2s block time) // [!code focus]
        },
      },
    },
  },
});
```

[Read more](/docs/config/contracts#chain) in the contracts guide.

## Block range

The `startBlock` and `endBlock` options for block intervals work the same way as they do for contracts.

[Read more](/docs/config/contracts#block-range) in the contracts guide.