FAQ

Authentication & Access

• How do I get an API key for OP Mainnet? Sign up at TheRPC.io, open the Dashboard, go to API Keys, and generate one. Drop it into https://optimism.therpc.io/YOUR_API_KEY and the Authorization: Bearer header.
• Can I create multiple API keys? Yes. Separate keys per app and per environment (development, staging, production) let you track usage independently and revoke one without disrupting the others.
• What if a key is compromised? Revoke it immediately from the dashboard, then generate a fresh key and update your services. Because each request is authenticated on its own, the old key stops working the moment it's revoked.

API Usage

• HTTP vs WebSocket on OP Mainnet? Use the HTTP endpoint (https://optimism.therpc.io/YOUR_API_KEY) for single, stateless requests and simple integrations. Use the WebSocket endpoint (wss://optimism.therpc.io/YOUR_API_KEY) for real-time subscriptions via eth_subscribe, such as streaming new ~2-second blocks instead of polling.
• How do I handle rate limits? Catch the rate-limit error, retry with exponential backoff, and if you hit limits regularly, consider upgrading your plan for higher throughput.
• Recommended timeouts? Around 30 seconds for HTTP requests, a 60-second ping/pong interval to keep WebSocket connections alive, and roughly 30 seconds for subscription operations.

Error Handling

OP Mainnet returns standard JSON-RPC error codes, summarized in the table below: -32700 for a parse error, -32600 for an invalid request, -32601 for a method that isn't found, -32602 for invalid params, -32603 for an internal error, and the -32000 to -32099 range for server errors. Four habits make error handling reliable: always check the error field before reading result, retry transient failures with exponential backoff, log the full error code and message for diagnosis, and set sensible timeouts so a slow request doesn't hang your application.

Common Error Response

1{
2  "jsonrpc": "2.0",
3  "error": {
4    "code": -32601,
5    "message": "Method not found"
6  },
7  "id": 1
8}

Standard JSON-RPC Error Codes

Technical Questions

• Tracking pending transactions: Poll eth_getTransactionReceipt until it returns a non-null receipt, or subscribe to newHeads and pending transactions via eth_subscribe for real-time updates — well suited to OP Mainnet's ~2-second blocks.
• Ensuring request ordering: Sequence transactions from an address with the correct nonce, fetched via eth_getTransactionCount, and use an application-level queue so you submit them in order rather than racing concurrent sends.
• Handling chain reorganizations: Wait for several confirmations by watching eth_blockNumber, listen to newHeads through eth_subscribe to detect new tips, and confirm a block is still canonical with eth_getBlockByNumber before treating a transaction as final.

Transaction Tracking Example

1// Example of transaction tracking
2const receipt = await web3.eth.getTransactionReceipt(txHash);
3if (receipt) {
4  console.log(`Transaction confirmed in block ${receipt.blockNumber}`);
5}

Performance

• Optimizing API usage: Combine reads into batch requests, switch to WebSocket subscriptions for real-time data instead of tight polling, cache slowly-changing values like contract bytecode, and tune polling intervals to OP Mainnet's ~2-second block cadence so you don't over-request.
• High-throughput best practices: Reuse connections with connection pooling, queue requests to smooth out bursts, monitor your rate-limit headers and dashboard metrics, and talk to us about dedicated infrastructure if your workload demands consistently high volume.

Network Specific

• Switching between networks: Change only the endpoint host — the same API key and JSON-RPC request format work across every chain TheRPC serves. After switching, confirm you're on the right network with net_version.
• Does the same code work everywhere? Yes. The same client code runs against OP Mainnet and any other supported chain; you just point it at a different endpoint. OP Mainnet's chain ID is 10 (hex 0xa), which you can verify at any time with eth_chainId.

Development & Integration

• Recommended Web3 libraries: For JavaScript use web3.js or ethers.js, for Python use web3.py, and for Java use web3j — all work with OP Mainnet unchanged thanks to its Ethereum equivalence. See Tools & SDKs for other languages.
• Testing your integration: Start against a testnet such as OP Sepolia, use a dedicated test API key, build in error handling from the start, validate connectivity with a simple eth_blockNumber call, and monitor latency and throughput before moving to OP Mainnet in production.