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

# Slot & Block Monitoring with LaserStream

> Monitor Solana network consensus, block production, and network state changes with LaserStream — slot timing, block metadata, and filtered full blocks.

Slot and block monitoring gives you a window into Solana's network consensus, block production timing, and overall health. With LaserStream you can track slot progression, block finalization, and network performance metrics in real-time using the [`helius-laserstream`](/laserstream/clients) SDK.

<Info>
  **Prerequisites:** This guide assumes you've completed the [LaserStream gRPC Quickstart](/laserstream/grpc) and have an API key.
</Info>

***

## Monitoring Types

<Tabs>
  <Tab title="Slot Updates">
    **Track network consensus progression**

    Monitor slot advancement across commitment levels:

    ```typescript theme={"system"}
    import { subscribe, CommitmentLevel, LaserstreamConfig, SubscribeRequest } from 'helius-laserstream';

    const subscriptionRequest: SubscribeRequest = {
      slots: {
        slotSubscribe: {
          filterByCommitment: false // Receive all commitment levels
        }
      },
      commitment: CommitmentLevel.CONFIRMED,
      accounts: {}, transactions: {}, transactionsStatus: {},
      blocks: {}, blocksMeta: {}, entry: {}, accountsDataSlice: [],
    };
    ```

    **Slot data includes:** slot number, parent slot, commitment status (`processed` / `confirmed` / `finalized`), and leader information.

    <Note>
      **Best for:** Network health monitoring, slot timing analysis, consensus tracking.
    </Note>
  </Tab>

  <Tab title="Block Data">
    **Monitor complete block information**

    Stream full blocks with transactions and account updates:

    ```typescript theme={"system"}
    const subscriptionRequest: SubscribeRequest = {
      blocks: {
        blockSubscribe: {
          accountInclude: [], // All accounts
          includeTransactions: true,
          includeAccounts: true,
          includeEntries: false
        }
      },
      commitment: CommitmentLevel.CONFIRMED,
      accounts: {}, transactions: {}, transactionsStatus: {},
      slots: {}, blocksMeta: {}, entry: {}, accountsDataSlice: [],
    };
    ```

    **Block data includes:** block metadata, transactions, account updates, block timing.

    <Warning>
      **High volume:** Full block streams generate significant data. Use `accountInclude` filters to reduce volume.
    </Warning>
  </Tab>

  <Tab title="Block Metadata">
    **Lightweight block information**

    Get block metadata without transaction details:

    ```typescript theme={"system"}
    const subscriptionRequest: SubscribeRequest = {
      blocksMeta: {
        blockMetaSubscribe: {}
      },
      commitment: CommitmentLevel.CONFIRMED,
      accounts: {}, transactions: {}, transactionsStatus: {},
      slots: {}, blocks: {}, entry: {}, accountsDataSlice: [],
    };
    ```

    **Metadata includes:** block hash, parent hash, slot, height, transaction count, rewards.

    <Tip>
      **Efficient:** Lower-bandwidth alternative to full block streaming.
    </Tip>
  </Tab>
</Tabs>

***

## Practical Examples

### Example 1: Network Health Monitor

Track slot progression and identify network issues:

```typescript [expandable] theme={"system"}
import { subscribe, CommitmentLevel, LaserstreamConfig, SubscribeRequest } from 'helius-laserstream';

let lastSlot = 0;
let lastTimestamp = Date.now();
const slotTimes: number[] = [];

// CommitmentLevel only ships the forward (name → number) mapping, so we keep
// a small reverse lookup for the numeric status the SDK returns on slot updates.
const STATUS_NAMES = ['PROCESSED', 'CONFIRMED', 'FINALIZED'] as const;

async function monitorNetworkHealth() {
  const subscriptionRequest: SubscribeRequest = {
    slots: {
      slotSubscribe: {
        filterByCommitment: true // Track processed commitment levels
      }
    },
    commitment: CommitmentLevel.PROCESSED,
    accounts: {}, transactions: {}, transactionsStatus: {},
    blocks: {}, blocksMeta: {}, entry: {}, accountsDataSlice: [],
  };

  const config: LaserstreamConfig = {
    apiKey: 'YOUR_API_KEY',
    endpoint: 'https://laserstream-mainnet-ewr.helius-rpc.com',
  };

  await subscribe(config, subscriptionRequest, async (data) => {
    if (!data.slot) return;
    const slot = data.slot;
    // The SDK returns u64 fields as strings to preserve precision.
    const currentSlot = Number(slot.slot);
    const currentTime = Date.now();

    console.log(`\n📊 Slot Update:`);
    console.log(`  Slot: ${currentSlot}`);
    console.log(`  Parent: ${slot.parent}`);
    // slot.status is a numeric enum (0=processed, 1=confirmed, 2=finalized).
    console.log(`  Status: ${STATUS_NAMES[slot.status] ?? slot.status}`);

    if (lastSlot > 0) {
      const slotDiff = currentSlot - lastSlot;
      const timeDiff = currentTime - lastTimestamp;

      if (slotDiff === 1) {
        slotTimes.push(timeDiff);
        if (slotTimes.length > 100) slotTimes.shift();

        const avg = slotTimes.reduce((a, b) => a + b, 0) / slotTimes.length;
        console.log(`  Slot Time: ${timeDiff}ms`);
        console.log(`  Avg Slot Time: ${avg.toFixed(1)}ms`);

        if (timeDiff > 800) {
          console.log(`  ⚠️  SLOW SLOT: ${timeDiff}ms (normal ~400ms)`);
        }
      } else if (slotDiff > 1) {
        console.log(`  ⚠️  SKIPPED ${slotDiff - 1} SLOTS`);
      }
    }

    lastSlot = currentSlot;
    lastTimestamp = currentTime;
  }, async (error) => {
    console.error('Stream error:', error);
  });
}

monitorNetworkHealth().catch(console.error);
```

### Example 2: Block Production Monitor

Track block production and transaction volume:

```typescript [expandable] theme={"system"}
async function monitorBlockProduction() {
  const subscriptionRequest: SubscribeRequest = {
    blocksMeta: {
      blockMetaSubscribe: {}
    },
    commitment: CommitmentLevel.CONFIRMED,
    accounts: {}, transactions: {}, transactionsStatus: {},
    slots: {}, blocks: {}, entry: {}, accountsDataSlice: [],
  };

  const config: LaserstreamConfig = {
    apiKey: 'YOUR_API_KEY',
    endpoint: 'https://laserstream-mainnet-ewr.helius-rpc.com',
  };

  await subscribe(config, subscriptionRequest, async (data) => {
    if (!data.blockMeta) return;
    const blockMeta = data.blockMeta;

    console.log(`\n🧱 Block Produced:`);
    console.log(`  Slot: ${blockMeta.slot}`);
    // blockHeight is a wrapper object: { blockHeight: '397657352' }
    console.log(`  Block Height: ${blockMeta.blockHeight?.blockHeight}`);
    console.log(`  Block Hash: ${blockMeta.blockhash}`);
    console.log(`  Parent Slot: ${blockMeta.parentSlot}`);
    console.log(`  Parent Hash: ${blockMeta.parentBlockhash}`);
    console.log(`  Transactions: ${blockMeta.executedTransactionCount}`);
    console.log(`  Entries: ${blockMeta.entriesCount}`);
    if (blockMeta.blockTime?.timestamp) {
      // blockTime.timestamp is a u64 as a string (Unix seconds).
      console.log(`  Block Time: ${new Date(Number(blockMeta.blockTime.timestamp) * 1000).toISOString()}`);
    }

    // rewards is a wrapper object: { rewards: [...], numPartitions: number | null }
    if (blockMeta.rewards?.rewards?.length > 0) {
      console.log(`  Rewards:`);
      blockMeta.rewards.rewards.forEach((r: any) => {
        console.log(`    ${r.pubkey}: ${r.lamports} lamports (${r.rewardType})`);
      });
    }

    if (Number(blockMeta.executedTransactionCount) > 3000) {
      console.log(`  🔥 HIGH ACTIVITY: ${blockMeta.executedTransactionCount} transactions`);
    }
  }, async (error) => {
    console.error('Stream error:', error);
  });
}
```

### Example 3: Filtered Block Monitor

Monitor blocks containing specific program activity:

```typescript [expandable] theme={"system"}
async function monitorDEXBlocks() {
  const subscriptionRequest: SubscribeRequest = {
    blocks: {
      blockSubscribe: {
        accountInclude: [
          "675kPX9MHTjS2zt1qfr1NYHuzeLXfQM9H24wFSUt1Mp8", // Raydium
          "CAMMCzo5YL8w4VFF8KVHrK22GGUsp5VTaW7grrKgrWqK", // Raydium CLMM
          "JUP6LkbZbjS1jKKwapdHNy74zcZ3tLUZoi5QNyVTaV4"   // Jupiter
        ],
        includeTransactions: true,
        includeAccounts: false,
        includeEntries: false
      }
    },
    commitment: CommitmentLevel.CONFIRMED,
    accounts: {}, transactions: {}, transactionsStatus: {},
    slots: {}, blocksMeta: {}, entry: {}, accountsDataSlice: [],
  };

  const config: LaserstreamConfig = {
    apiKey: 'YOUR_API_KEY',
    endpoint: 'https://laserstream-mainnet-ewr.helius-rpc.com',
  };

  await subscribe(config, subscriptionRequest, async (data) => {
    if (!data.block) return;
    const block = data.block;

    let successfulDexTx = 0;
    let totalFees = 0; // lamports
    block.transactions?.forEach((tx: any) => {
      if (tx.meta && !tx.meta.err) {
        successfulDexTx++;
        // tx.meta.fee is a u64 string — coerce before adding.
        totalFees += Number(tx.meta.fee ?? 0);
      }
    });

    console.log(`\n🔄 DEX Activity Block:`);
    console.log(`  Slot: ${block.slot}`);
    console.log(`  Block Height: ${block.blockHeight?.blockHeight}`);
    console.log(`  Block Hash: ${block.blockhash}`);
    console.log(`  Total transactions in block: ${block.executedTransactionCount}`);
    console.log(`  Matched DEX transactions: ${block.transactions?.length ?? 0}`);
    console.log(`  Successful DEX transactions: ${successfulDexTx}`);
    if (successfulDexTx > 0) {
      console.log(`  Total Fees: ${(totalFees / 1e9).toFixed(4)} SOL`);
      console.log(`  Avg Fee: ${(totalFees / successfulDexTx / 1e9).toFixed(6)} SOL`);
    }
  }, async (error) => {
    console.error('Stream error:', error);
  });
}
```

***

## Data Structures

<Accordion title="Slot Data Structure">
  ```typescript theme={"system"}
  {
    slot: string;     // Current slot number (u64 as string)
    parent: string;   // Parent slot number (u64 as string)
    status: number;   // CommitmentLevel enum: 0 = processed, 1 = confirmed, 2 = finalized
  }
  ```

  Each slot represents \~400ms of network time. The three commitment levels reflect progressively stronger guarantees: `processed` (initial), `confirmed` (supermajority voted), `finalized` (irreversible).

  <Tip>
    u64 fields (slot, parent) arrive as strings to preserve precision beyond `Number.MAX_SAFE_INTEGER`. Convert with `Number(slot.slot)` when you need arithmetic. `status` is a numeric enum — use `CommitmentLevel[slot.status]` for the human-readable name.
  </Tip>
</Accordion>

<Accordion title="Block Metadata Structure">
  ```typescript theme={"system"}
  {
    slot: string;                                  // u64 as string
    blockhash: string;
    rewards: {
      rewards: Array<{
        pubkey: string;
        lamports: string;                          // u64 as string
        rewardType: string;                        // "fee" | "rent" | "voting" | "staking"
      }>;
      numPartitions: number | null;
    };
    blockTime: { timestamp: string };              // Unix seconds as a u64 string
    blockHeight: { blockHeight: string };          // u64 as string, wrapped
    parentSlot: string;                            // u64 as string
    parentBlockhash: string;
    executedTransactionCount: string;              // u64 as string
    entriesCount: string;                          // u64 as string
  }
  ```

  <Tip>
    Numeric fields (slot, parentSlot, executedTransactionCount, entriesCount, the values inside `blockHeight` and `blockTime`) are emitted as strings because they are u64 in the underlying proto. Wrap them in `Number(...)` for arithmetic or comparisons.
  </Tip>
</Accordion>

<Accordion title="Full Block Structure">
  ```typescript theme={"system"}
  {
    slot: string;                                  // u64 as string
    blockhash: string;
    rewards: {
      rewards: Array<{
        pubkey: string;
        lamports: string;                          // u64 as string
        rewardType: string;
      }>;
      numPartitions: number | null;
    };
    blockTime: { timestamp: string };              // Unix seconds (u64 string)
    blockHeight: { blockHeight: string };          // u64 as string, wrapped
    parentSlot: string;                            // u64 as string
    parentBlockhash: string;
    executedTransactionCount: string;              // total executed tx in the block (u64 as string)
    updatedAccountCount: string;                   // total account updates in the block (u64 as string)
    entriesCount: string;                          // u64 as string
    transactions: Array<{
      signature: Buffer;                           // base58-encode for display
      isVote: boolean;
      transaction: TransactionMessage;             // full transaction payload
      meta: TransactionMeta;                       // execution metadata (fee, err, balances, …)
      index: string;                               // u64 as string
    }>;
    accounts: AccountUpdate[];                     // populated when includeAccounts: true
    entries: Entry[];                              // populated when includeEntries: true
  }
  ```

  Full blocks can be several MB with all transactions and accounts. The same u64-as-string convention applies — wrap numeric fields with `Number(...)` for arithmetic. Inside each transaction, `meta.fee`, `meta.preBalances`, `meta.postBalances`, etc. are also strings.
</Accordion>

***

## Performance Considerations

<CardGroup cols={2}>
  <Card title="Slot Monitoring" icon="clock">
    Lightweight: very low bandwidth, minimal processing overhead. Good for monitoring dashboards.
  </Card>

  <Card title="Block Metadata" icon="info">
    Balanced: moderate bandwidth, block-level insights without full data. Suitable for analytics.
  </Card>

  <Card title="Full Blocks" icon="database">
    High volume: complete transaction data, requires robust processing. Always pair with filters.
  </Card>

  <Card title="Filtered Blocks" icon="filter">
    Optimized: use `accountInclude`, disable `includeAccounts`/`includeEntries` you don't need.
  </Card>
</CardGroup>

***

## Use Cases

<Tabs>
  <Tab title="Network Monitoring">
    Track network health and performance — slot timing, congestion, consensus.

    ```typescript theme={"system"}
    const targetSlotTime = 400; // ms
    const tolerance = 200; // ms
    if (Math.abs(slotTime - targetSlotTime) > tolerance) {
      console.log(`Network performance issue detected`);
    }
    ```
  </Tab>

  <Tab title="Analytics & Metrics">
    Collect blockchain analytics data — transaction volume, fee analysis, block size, activity patterns.

    ```typescript theme={"system"}
    const dailyStats = {
      date: new Date().toDateString(),
      totalTransactions: 0,
      totalFees: 0,
      blockCount: 0
    };
    ```
  </Tab>

  <Tab title="Application Synchronization">
    Keep applications in sync with the network — slot-based updates, block confirmations.

    ```typescript theme={"system"}
    if (data.slot && data.slot.status === 'finalized') {
      updateApplicationState(data.slot.slot);
    }
    ```
  </Tab>
</Tabs>

***

## Error Handling

<Accordion title="Missing Slots">
  **Symptom:** Gaps in slot progression.

  **Causes:** Network connectivity issues, validator downtime, client processing delays.

  **Solutions:** Track slot gaps and alert; implement catch-up logic via [historical replay](/laserstream/historical-replay); monitor connection health.
</Accordion>

<Accordion title="High Volume">
  **Symptom:** Too much block data.

  **Solutions:** Use block metadata instead of full blocks; apply account filters; disable unnecessary inclusions (entries, accounts); process asynchronously.
</Accordion>

<Accordion title="Timing Issues">
  **Symptom:** Inconsistent slot timing.

  **Analysis:** Calculate moving averages; track deviations; monitor network health metrics; correlate with validator performance.
</Accordion>

***

## Best Practices

<Note>
  **Production Guidelines:**

  * **Start with metadata** — use block metadata before subscribing to full blocks
  * **Apply filters** — use `accountInclude` to drop irrelevant data
  * **Monitor timing** — track slot progression as a network-health canary
  * **Handle gaps** — combine with [historical replay](/laserstream/historical-replay) so missing slots are auto-backfilled on reconnect
  * **Process async** — don't block stream processing with heavy computations
  * **Match commitment to need** — `processed` for low-latency UIs, `confirmed`/`finalized` for state writes
</Note>

***

## Next Steps

<CardGroup cols={2}>
  <Card title="Transaction Monitoring" icon="receipt" href="/laserstream/guides/transaction-monitoring">
    Filter transactions by program, account, vote, or failure status.
  </Card>

  <Card title="Stream Pump AMM Data" icon="chart-line" href="/laserstream/guides/stream-pump-amm-data">
    Real-world example: monitor Pump AMM transactions.
  </Card>

  <Card title="Decoding Transaction Data" icon="binary" href="/laserstream/guides/decoding-transaction-data">
    Parse the binary `transactionUpdate` payloads into readable Solana transactions.
  </Card>

  <Card title="Yellowstone protocol reference" icon="book" href="/grpc/slot-and-block-monitoring">
    The same workflow against the raw Yellowstone gRPC protocol.
  </Card>
</CardGroup>