RPC Node

The primary interface is a JSON-RPC API, a stateless, lightweight protocol where clients send requests as JSON objects and receive JSON responses. Key methods include:

• eth_getBalance: Query an account's balance.
• eth_sendRawTransaction: Broadcast a signed transaction.
• eth_getLogs: Retrieve event logs from smart contracts. This standardized API allows wallets, dApps, and explorers to communicate with the blockchain network uniformly.

The node provides read-only access to the current and historical state of the blockchain. This includes:

• Account Balances & Nonces: The native token holdings and transaction count for any address.
• Smart Contract Storage & Code: The stored data and bytecode of deployed contracts.
• Block & Transaction Data: Details of any block, transaction, or transaction receipt. These queries are essential for applications to display accurate, real-time information without running a full node themselves.

A core function is accepting signed transactions from users and propagating them to the network's peer-to-peer (P2P) layer. The node:

1. Validates the transaction's basic format and signature.
2. Adds it to its local mempool (memory pool) of pending transactions.
3. Broadcasts it to its connected peers, who then propagate it further. This service is critical for initiating any on-chain state change, from simple transfers to complex contract interactions.

Beyond simple request-response, advanced nodes support WebSocket connections for real-time event subscriptions. Clients can subscribe to specific events, such as:

• New Blocks: newHeads notification when a block is mined.
• Pending Transactions: newPendingTransactions for mempool activity.
• Contract Logs: logs for specific smart contract events. This push-based model is vital for applications requiring instant updates, like trading dashboards or notification systems.

The node enforces network segregation by its configured Chain ID. This prevents transaction replay attacks across different networks (e.g., Ethereum Mainnet vs. a testnet). It ensures that:

• Transactions signed for one chain are invalid on another.
• Clients interact with the intended blockchain.
• The correct native currency and gas pricing are used. This is a fundamental security and operational feature.

To help users create viable transactions, the node provides gas estimation services. Key methods include:

• eth_estimateGas: Estimates the gas units required for a transaction.
• eth_gasPrice: Suggests a gas price based on current network congestion.
• eth_feeHistory (EIP-1559): Provides historical base fee and priority fee data. This data is crucial for wallets and dApps to set appropriate transaction fees that will be processed in a timely manner.

These methods retrieve data about the current and historical state of the blockchain.

• eth_getBalance: Returns the Ether balance of a given address.
• eth_getBlockByNumber: Fetches a full block by its number (e.g., "latest", "0x1").
• eth_call: Executes a message call (a read-only function) on a smart contract without creating a transaction.
• eth_getTransactionReceipt: Gets the receipt of a transaction by hash, including status and gas used.

Methods for creating and submitting transactions to the network.

• eth_sendTransaction: Creates, signs, and sends a new transaction (requires the account to be unlocked on the node).
• eth_sendRawTransaction: Broadcasts a signed raw transaction to the network. This is the standard method for dApps and wallets, as signing happens client-side.
• eth_estimateGas: Estimates the gas units required for a transaction before sending it.

Methods that provide metadata about the node and the network it's connected to.

• net_version: Returns the current network ID (e.g., "1" for Ethereum Mainnet).
• eth_chainId: Returns the EIP-155 chain ID for the current network.
• eth_syncing: Returns data on the synchronization status of the node.
• web3_clientVersion: Returns the client software version (e.g., Geth, Erigon).

Methods for subscribing to or querying on-chain events emitted by smart contracts.

• eth_getLogs: Returns an array of event logs matching a given filter object (e.g., from a specific contract address and topic).
• eth_newFilter: Creates a filter object to listen for specific logs. Used with eth_getFilterChanges.
• eth_newBlockFilter: Creates a filter to notify when new blocks are mined. Note: WebSocket subscriptions (eth_subscribe) are often preferred for real-time events.

A practical JSON-RPC request and response for getting an account balance.

Request:

jsonCopy
{
  "jsonrpc": "2.0",
  "method": "eth_getBalance",
  "params": ["0x742d35Cc6634C0532925a3b844Bc9e90F1A904A2", "latest"],
  "id": 1
}

Response:

jsonCopy
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x1a055690d9db80000"
}

The result is the balance in wei (the smallest Ether unit).

A load balancer is a critical infrastructure component that distributes incoming RPC requests across a pool of backend nodes. This is essential for production RPC services to achieve:

• High Availability: If one node fails, traffic is routed to healthy ones.
• Scalability: Handles request volumes beyond a single node's capacity.
• Performance: Distributes load to prevent any single node from being overwhelmed. Common strategies include round-robin, least connections, and geographic routing.

A WebSocket endpoint provides a persistent, full-duplex communication channel between a client and an RPC node, as opposed to the one-off request-response model of HTTP. This is crucial for subscribing to real-time blockchain events without constant polling. Common use cases include:

• Listening for new blocks (eth_subscribe, newHeads).
• Tracking pending transaction mempool activity.
• Receiving instant notifications for specific smart contract events.