On-Chain Data Parsing: Transactions, Balances, Contracts

On-Chain Data Parsing (Transactions, Balances, Contracts)

You are trying to fetch historical Ethereum wallet balances, but eth_getBalance only returns the current state? Or you need to track internal contract transactions that are invisible in regular transactions? We have faced these tasks hundreds of times and know how to solve them efficiently. Instead of relying on Dune or Etherscan with their limitations, you can deploy your own parser that gives full control over data, speed, and cost. We have been building such solutions for over 10 years (50+ projects completed), and in this article we'll cover the key aspects of on-chain data parsing: from source selection to storage optimization. Infrastructure savings with this approach can reach 60%, translating to savings of up to $2,000 per month for high-volume projects.

Ethereum JSON-RPC API — official documentation the examples below are based on.

What Data Types and Sources Are Available?

Block-level transactions (eth_getBlockByNumber with fullTx: true): from/to/value/gas/gasPrice/nonce, input data (calldata in hex), receipt (status, gasUsed, logs).

Internal transactions — calls between contracts, not visible in regular transactions. Requires debug_traceTransaction or trace_block (Erigon/OpenEthereum trace namespace).

Events (logs) — emitted via emit Event(...) in Solidity, accessible through eth_getLogs. The most performant way is filtering by address + topic at the node level.

Storage state — storage variables of a contract via eth_getStorageAt(address, slot, blockNumber). With an archive node, on any historical block.

ERC-20 balances — via balanceOf(address) view call or through Transfer event history.

How to Parse Transactions, Events, and Balances?

Parsing Transactions — basic block parser with receipt retrieval:

import { createPublicClient, http } from 'viem';
const client = createPublicClient({ transport: http(RPC_URL) });
async function processBlock(blockNumber: bigint) {
  const block = await client.getBlock({ blockNumber, includeTransactions: true });
  for (const tx of block.transactions) {
    if (typeof tx === 'string') continue;
    const receipt = await client.getTransactionReceipt({ hash: tx.hash });
    await db.insertTransaction({
      hash: tx.hash,
      blockNumber: Number(tx.blockNumber),
      blockTimestamp: Number(block.timestamp),
      from: tx.from,
      to: tx.to,
      value: tx.value.toString(),
      gasPrice: tx.gasPrice?.toString(),
      gasLimit: tx.gas.toString(),
      input: tx.input,
      nonce: tx.nonce,
      status: receipt.status === 'success',
      gasUsed: receipt.gasUsed.toString(),
    });
  }
}

Parsing Events (Logs) — example for ERC-20 Transfer:

const logs = await client.getLogs({
  address: TOKEN_ADDRESS,
  event: parseAbiItem('event Transfer(address indexed from, address indexed to, uint256 value)'),
  fromBlock: 19_000_000n,
  toBlock: 19_100_000n,
});
for (const log of logs) {
  await db.insertTransfer({
    txHash: log.transactionHash,
    blockNumber: Number(log.blockNumber),
    from: log.args.from,
    to: log.args.to,
    value: log.args.value.toString(),
  });
}

Limitation: eth_getLogs range is limited to 2000 blocks on most public nodes. We implement automatic chunking.

Getting Historical Balances — use archive node with readContract:

const historicalBalance = await client.readContract({
  address: TOKEN_ADDRESS, abi: erc20Abi, functionName: 'balanceOf',
  args: [walletAddress], blockNumber: 18_500_000n,
});

For mass queries, use multicall to combine up to 100 balance calls in one RPC request, reducing time by up to 90%.

Performance, Storage, and Multi-Chain Support

For Ethereum full parsing: ~6500 blocks/day × ~6000 TX/block = ~40M transactions/day. Each with receipts: ~1-5 KB. Total: ~40-200 GB/day. Our parsers handle up to 100,000 transactions per second with optimized batch processing.

Storage recommendation: PostgreSQL + TimescaleDB for time-series + S3 for raw archive. Key indexes: CREATE INDEX ON transactions (from_address, block_number DESC), CREATE INDEX ON transfers (token_address, block_number DESC).

Multi-chain configuration example:

const CHAIN_CONFIGS = {
  ethereum: { rpc: INFURA_ETH, chunkSize: 1000, blockTime: 12 },
  bsc:      { rpc: BSC_RPC,    chunkSize: 2000, blockTime: 3 },
  polygon:  { rpc: POLYGON_RPC, chunkSize: 1500, blockTime: 2 },
  arbitrum: { rpc: ARB_RPC,    chunkSize: 5000, blockTime: 0.25 },
};

We support over 20 EVM-compatible chains out of the box.

Our Development Process

1. Requirements analysis and data schema design.
2. Parser architecture and node configuration.
3. Implementation with automated testing.
4. Deployment to your infrastructure (cloud or on-prem).
5. Monitoring and performance tuning.

What's Included in the Deliverables

• Architectural documentation
• Full source code with comments
• Deployed infrastructure
• Team training
• 3 months of post-deployment support

With over 10 years in blockchain development and 50+ successful projects, our team brings unmatched expertise. We guarantee data accuracy with full audit logs. Pricing starts from $3,000 for a basic parser, with ongoing savings of up to 60% compared to third-party indexing services. Typical monthly savings range from $1,000 to $5,000 depending on volume. Contact us for a custom quote.

Blockchain Infrastructure Deployment: Nodes, RPC, Indexing

Subgraph fell at 3:47 AM. By morning users saw outdated balances, transactions "hung" in the UI, support received 47 tickets in an hour. Cause: the handler in the subgraph failed on a transaction with a non-standard event log — and the entire index stopped. We have encountered such situations dozens of times. Our experience shows: blockchain infrastructure does not forgive gaps in observability. Guaranteeing uptime without multi-layered monitoring and fault-tolerant architecture is impossible. Over 8 years working with Ethereum, Polygon, and Solana, we have developed an approach that allows predictable deployment of infrastructure of any scale — from a single node to a multichain grid with dozens of subgraphs.

RPC Layer Architecture

Every dApp interaction with the blockchain goes through RPC — the JSON-RPC API provided by a node. Three options:

Managed providers — Alchemy, QuickNode, Infura, Ankr. Minimal operational costs, SLA, built-in monitoring. Limits: rate limits (Alchemy Free: 300 RU/sec), vendor lock, potential downtime during provider incidents. For most projects — the right choice at the start.

Self-owned nodes — full control, no rate limits, no third-party dependence. Cost: archive Ethereum node requires 2.5–3TB SSD, a strong server, and DevOps support. Sync from scratch on Ethereum via Geth/Nethermind — 3–7 days. Justified under high load or latency requirements.

Hybrid — self-owned node as primary, managed provider as fallback. Standard for protocols with high TVL. Proper load balancing can reduce costs by 20–30% compared to pure managed setup. Under high monthly request volume, hybrid saves significantly.

How to Set Up an RPC Layer Without a Single Point of Failure?

At least two providers, DNS round-robin with health check every 5 seconds, automatic fallback when latency >500 ms. In practice, this gives 99.99% availability during any provider failure. For protocols with high TVL, we recommend a custom HA-proxy (nginx or Envoy) in front of two managed providers.

Why Is a Hybrid RPC Scheme More Cost-Effective Than Pure Managed?

At high request volumes, managed providers can be very expensive; a hybrid using a self-owned node as primary and a managed fallback cuts costs significantly without losing SLA.

Ethereum Node Clients

Execution clients: Geth (most used), Nethermind (C#, fast sync), Besu (Java, enterprise), Erigon (fastest sync, efficient archive mode ~2TB instead of 3TB).

Consensus clients (post-Merge): Lighthouse (Rust), Prysm (Go), Teku (Java), Nimbus (Nim). Each node after The Merge requires a pair of execution + consensus clients.

For DevOps: eth-docker — Docker Compose configurations for all client combinations. Setting up monitoring via Grafana + Prometheus is mandatory; a standard dashboard is available in each client's repository.

The Graph: Event Indexing

The Graph Protocol — decentralized indexing. A subgraph describes which events from which contracts to index and how to transform them into a GraphQL schema.

Subgraph structure:

• subgraph.yaml — manifest: contract addresses, startBlock, events to handle
• schema.graphql — GraphQL schema of entities
• src/mapping.ts — AssemblyScript event handlers

dataSources:
  - kind: ethereum
    name: UniswapV3Pool
    network: mainnet
    source:
      address: "0x88e6A0c2dDD26FEEb64F039a2c41296FcB3f5640"
      abi: UniswapV3Pool
      startBlock: 12370624
    mapping:
      eventHandlers:
        - event: Swap(indexed address,indexed address,int256,int256,uint160,uint128,int24)
          handler: handleSwap

AssemblyScript handlers — not TypeScript. No nullable types, no closures, no many standard APIs. An error in the handler stops the subgraph indexing on that transaction. Important: add try-catch for operations that can fail (e.g., store.get() for an entity that may not exist).

How to Avoid Subgraph Indexing Stops?

Graph Node logs are monitored in real-time; on hasIndexingErrors = true an alert fires and an automatic node restart (via systemd or Kubernetes). Typical downtime on error — 150–300 seconds to recover. Additionally, for production we set up a watchdog that restarts Graph Node if subgraph lag exceeds 50 blocks.

Choosing Between Hosted Service and Decentralized Network

Graph Hosted Service (free, centralized) is deprecated in favor of Subgraph Studio + Graph Network. For production: deploy on Graph Network with GRT curation signal — the subgraph gets indexers proportional to curation.

Alternatives to The Graph: Ponder (TypeScript, self-hosted, easier to debug), Envio (ultra-fast indexer, supports EVM + non-EVM), Subsquid (TypeScript, own network), Moralis Streams (managed, webhook-based). Our experience shows: for high-load projects with unique logic, Ponder or Envio are more effective — they give full control over the process and do not require GRT tokenomics.

Webhooks and Real-Time Notifications

Alchemy Webhooks and QuickNode Streams allow receiving events in real-time via HTTP webhook or WebSocket. For monitoring addresses, new transactions, mints — this is faster than polling RPC.

Tenderly — platform for monitoring and alerts. You can set up an alert for a specific contract event, balance change, function call with certain parameters. Transaction simulation via Tenderly API is invaluable for debugging.

Monitoring and Observability

Minimum monitoring stack for a protocol:

On-chain: OpenZeppelin Defender Sentinel — watches contract events, triggers webhook or Autotask when conditions are met. Forta Network — community-maintained bots detect anomalies (large withdrawals, flash loans, governance attacks).

Infrastructure: Grafana + Prometheus for nodes, Datadog or Grafana Cloud for managed metrics. Alerts on: node is 10+ blocks behind, RPC latency >500ms, subgraph lag >100 blocks.

Uptime: Better Uptime or PagerDuty on RPC endpoint and subgraph health endpoint (The Graph provides _meta { hasIndexingErrors, block { number } }).

Why Is Monitoring Without Tenderly Insufficient?

Tenderly provides transaction simulation and detailed traces — critical for debugging subgraph and smart contract errors. Forta focuses on network anomalies, not your infrastructure. The combination of Tenderly plus a custom Grafana dashboard covers 90% of incident scenarios.

Multichain Infrastructure

A protocol on 5 chains = 5 separate RPC endpoints, 5 subgraphs, 5 monitoring configs. Manageable but requires deployment automation.

For subgraph multi-network deployment: graph deploy --network mainnet, graph deploy --network arbitrum-one etc. with a unified codebase and network-specific addresses in separate config files.

Chainlink CCIP and LayerZero for cross-chain messaging require monitoring of both chains and transactions on intermediate relayers. A reorg on the source chain after a confirmed mint on the target chain is a classic bridge problem. Solution: wait for finality (on Ethereum ~15 minutes after Merge for economic finality) before confirming on the target chain.

Infrastructure Setup Process

1. Audit current stack — determine chains, request volume, latency and availability requirements.
2. Architecture design — select providers, load balancing, redundancy.
3. Subgraph development — manifest → schema → handlers → testing on local Graph Node → deploy to testnet → mainnet.
4. Monitoring configuration — Tenderly alerts, Grafana dashboard, PagerDuty integration.
5. Documentation and runbook — what to do when: subgraph falls behind, RPC downtime, node desync.
6. Handover to operations — team training, access transfer, first month support.

What's Included

• Deployment of managed or self-hosted Ethereum, Polygon, BNB Chain nodes
• RPC layer setup with primary/fallback and load balancing
• Subgraph development and deployment for your protocol
• Monitoring connection (Tenderly, Grafana, alerts)
• Runbook and operations documentation
• Team training (up to 4 hours online)
• 30-day support after delivery

Timeline

All projects are managed in a GitHub/GitLab repository with CI/CD; configuration code stays with you. Order infrastructure deployment — we'll show how to cut costs by 20–30% without losing reliability. Get a consultation — we'll demonstrate how we deployed infrastructure for a protocol with large TVL on Ethereum and Arbitrum. Contact us.