Multi-chain dApp backend with Blockmetric RPC

// Multi-chain dApp backend with Blockmetric RPC and ethers v6: the native balance of one address on every chain, the
// latest block per chain, and incoming token transfers read in log ranges the chain allows. One token for all chains.
//
//   npm install ethers
//   export BLOCKMETRIC_RPC_URL=https://rpc.<domain>     # shown on Account > RPC
//   export BLOCKMETRIC_RPC_TOKEN=...                    # your endpoint token (keep it on the server)
//   ADDRESS=0x... node balances-ethers.mjs
//
// Credits: every JSON-RPC call is 1 request (a batch of 8 calls counts as 8). eth_getLogs covers at most 10,000 blocks
// per call (HyperEVM: 50), so wide ranges are read in steps.
import { Contract, JsonRpcProvider, formatEther, formatUnits, id, zeroPadValue } from 'ethers'

const RPC = (process.env.BLOCKMETRIC_RPC_URL ?? '').replace(/\/+$/, '')
const TOKEN = process.env.BLOCKMETRIC_RPC_TOKEN
if (!RPC || !TOKEN) throw new Error('Set BLOCKMETRIC_RPC_URL and BLOCKMETRIC_RPC_TOKEN')
const ADDRESS = process.env.ADDRESS ?? '0x0000000000000000000000000000000000000000'

// slug, chain id, gas token, eth_getLogs block limit
const CHAINS = [
  ['eth', 1, 'ETH', 10_000],
  ['base', 8453, 'ETH', 10_000],
  ['arbitrum', 42161, 'ETH', 10_000],
  ['optimism', 10, 'ETH', 10_000],
  ['polygon', 137, 'POL', 10_000],
  ['bsc', 56, 'BNB', 10_000],
  ['avalanche', 43114, 'AVAX', 10_000],
  ['hyperevm', 999, 'HYPE', 50],
]

// staticNetwork: the chain id is known, so ethers skips a network lookup on every start (saves a request each time).
const provider = (slug, chainId) => new JsonRpcProvider(`${RPC}/${slug}/${TOKEN}`, chainId, { staticNetwork: true, batchMaxCount: 10 })

// 1. Balance and head block on every chain, in parallel (ethers batches the two calls per chain into one HTTP request).
const rows = await Promise.all(
  CHAINS.map(async ([slug, chainId, symbol]) => {
    const p = provider(slug, chainId)
    try {
      const [block, wei] = await Promise.all([p.getBlockNumber(), p.getBalance(ADDRESS)])
      return `${slug.padEnd(10)} block ${String(block).padStart(10)}  ${formatEther(wei)} ${symbol}`
    } catch (e) {
      return `${slug.padEnd(10)} ${e.shortMessage ?? e.message}` // 429: slow down; 403: chain or method not in your plan
    } finally {
      p.destroy()
    }
  }),
)
console.log(rows.join('\n'))

// 2. Incoming USDC transfers on Base over the last 20,000 blocks, read in steps of the chain's log limit.
const USDC_BASE = '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
const base = provider('base', 8453)
const usdc = new Contract(USDC_BASE, ['function decimals() view returns (uint8)'], base)
const decimals = await usdc.decimals()
const head = await base.getBlockNumber()
const filter = { address: USDC_BASE, topics: [id('Transfer(address,address,uint256)'), null, zeroPadValue(ADDRESS, 32)] }
let total = 0n
for (let from = head - 20_000; from <= head; from += 10_000) {
  const logs = await base.getLogs({ ...filter, fromBlock: from, toBlock: Math.min(from + 9_999, head) })
  for (const log of logs) total += BigInt(log.data)
}
console.log(`USDC received on Base in the last 20,000 blocks: ${formatUnits(total, decimals)}`)
base.destroy()