Blockchain indexing with The Graph: subgraph design and optimization

We often encounter situations where the frontend makes dozens of eth_call and getLogs calls on every page load. On mainnet this takes 2–3 seconds, over public RPC it's unreliable, and when aggregation or historical data is needed, direct calls become simply impossible. The Graph solves this problem correctly: you write a subgraph once, which indexes contract events, and get a GraphQL API with arbitrary queries in milliseconds. Infrastructure cost savings can reach 90% (up to $2000 per month for a typical DeFi project), and query speed increases tenfold. Below we'll break down how to design and write a subgraph to avoid common mistakes and achieve maximum performance.

How to design a subgraph schema?

A subgraph consists of three components, and it's critical to design the schema based on frontend queries, not based on the event structure.

• subgraph.yaml — manifest. Describes data sources: which contracts to listen to, starting block (startBlock), which events and functions to handle. Critical: startBlock must be the contract deployment block, not zero — otherwise indexing will take days.
• schema.graphql — entity types. This is what will be available via GraphQL. Design it based on frontend needs, not based on contract event structure — these are different things.
• mappings.ts — AssemblyScript handlers. Transform raw events into schema entities.

Schema design

The most common mistake is making the schema a mirror of contract events. If the event is Transfer(address from, address to, uint256 amount), you don't need a TransferEvent entity. Instead, think about queries: "what is the current balance of a user", "top holders", "volume in the last 24 hours".

type Token @entity {
  id: ID!
  totalSupply: BigInt!
  holderCount: Int!
}

type Account @entity {
  id: Bytes!
  balance: BigInt!
  transfersIn: [Transfer!]! @derivedFrom(field: "to")
  transfersOut: [Transfer!]! @derivedFrom(field: "from")
}

type Transfer @entity(immutable: true) {
  id: Bytes!
  from: Account!
  to: Account!
  amount: BigInt!
  blockNumber: BigInt!
  timestamp: BigInt!
}

@entity(immutable: true) for Transfer is an important optimization. Immutable entities are not stored in the undo buffer, making indexing 30–40% faster.

Handlers: step-by-step

AssemblyScript is not full TypeScript — there's no null via ?., no Array.from(), no standard JS methods. This is a frequent source of errors for developers coming from frontend.

1. Identify the event you are handling (e.g., Transfer).
2. Load or create an entity using Account.load(address) or new Account(address).
3. Update fields (balance, references).
4. Save changes via save().

// Correct loading or creating an entity
function getOrCreateAccount(address: Address): Account {
  let account = Account.load(address)
  if (account == null) {
    account = new Account(address)
    account.balance = BigInt.fromI32(0)
  }
  return account as Account
}

export function handleTransfer(event: TransferEvent): void {
  let from = getOrCreateAccount(event.params.from)
  let to = getOrCreateAccount(event.params.to)

  from.balance = from.balance.minus(event.params.value)
  to.balance = to.balance.plus(event.params.value)

  from.save()
  to.save()

  // Immutable — create once, never load
  let transfer = new Transfer(
    event.transaction.hash.concatI32(event.logIndex.toI32())
  )
  transfer.from = from.id
  transfer.to = to.id
  transfer.amount = event.params.value
  transfer.blockNumber = event.block.number
  transfer.timestamp = event.block.timestamp
  transfer.save()
}

Call handlers and block handlers

In addition to events, The Graph can handle function calls (callHandlers) and each block (blockHandlers). Call handlers are needed when the contract doesn't emit events for required operations — legacy contracts often lack events. Block handlers are used for periodic snapshots (e.g., daily stats). Both significantly slow down indexing, especially block handlers — use them only when necessary.

Why is The Graph faster than direct RPC calls?

Direct RPC calls execute sequentially and load the node. The Graph indexes data once and stores it in an optimized database accessible via GraphQL. Queries execute in milliseconds (typical time 50 to 200 ms), and pagination via first/skip works up to skip: 5000 — for larger datasets use keyset pagination with id_gt. According to The Graph documentation, indexing throughput can reach 1000 events per second on standard hardware. Infrastructure cost savings can reach 90%, as confirmed by experience of large DeFi projects — for example, Uniswap reduced RPC costs by $3000+ per month after switching to a subgraph.

Which hosting to choose: Hosted Service, Decentralized, or self-hosted?

The choice of subgraph deployment option depends on requirements for availability, control, and budget.

Our team, with ten years of experience in blockchain, has implemented over 20 The Graph integrations. We help you choose the optimal option for your project and avoid common problems.

Typical indexing issues

• Subgraph fails with "store error" — check non-nullable fields.
• Indexing stalls on a block — add handling for reverted transactions via receipt.status.
• Data discrepancy due to reorgs — set minEthereumBlockConfirmations.
• Excessive gas consumption when writing — use @entity(immutable: true) for immutable data.

What to know about pagination and filtering?

Keyset pagination is preferred for large datasets — it's faster and has no skip limit.

Frontend integration

Typical stack: Apollo Client or urql for React applications. The Graph supports subscriptions via WebSocket for real-time updates without polling.

const POSITIONS_QUERY = gql`
  query UserPositions($account: Bytes!, $skip: Int!) {
    positions(
      where: { owner: $account, liquidity_gt: "0" }
      orderBy: createdAt
      orderDirection: desc
      first: 100
      skip: $skip
    ) {
      id
      pool { token0 { symbol } token1 { symbol } feeTier }
      liquidity
      depositedToken0
      depositedToken1
    }
  }
`

Timelines and what's included

In 2–5 days: schema design tailored to client needs, writing mappings for all events and calls, testing on a fork, deployment to Hosted Service or setting up a self-hosted node, basic integration into existing frontend or providing a GraphQL endpoint. Cost is calculated individually, but savings on RPC queries justify the investment — typical payback occurs within 1–3 months.

Contact us to discuss integrating The Graph into your project. Experience with The Graph and dozens of successful integrations guarantee results. Request a consultation — we'll prepare a custom proposal.

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.