Five invariants for BNB Chain wallet indexers

BNB Chain wallet indexers should enforce five invariants: identify the chain, follow canonical blocks, distinguish provisional data, decode token events consistently and make replay safe. Together, these checks keep a wallet’s history tied to the chain’s records. For more on how chart views and wallet views relate to underlying records, see Poocoin’s guide to charts, wallets and chain data.

How should an indexer identify BNB Chain data?

Every indexed record should be scoped to a chain ID and a contract address. BNB Smart Chain mainnet uses chain ID 56, according to BNB Chain’s JSON-RPC documentation; the same address on another network is a different asset or account context.

Store the chain ID with each block, transaction, log and token record. Keep contract addresses in a consistent format, such as lowercase for lookup, while retaining the checksummed form for display.

How do blocks and wallet events stay in order?

Use block number, transaction index and log index to order events, and verify each block’s parent hash against the preceding indexed block. A height alone is not enough to identify a block if the chain’s canonical history changes.

For token activity, index contract-emitted transfer logs rather than guessing from transaction inputs. A transaction can call several contracts, so its sender and recipient do not necessarily describe every asset movement.

When should an indexer treat a block as final?

An indexer should label recent data provisional until it meets the application’s finality threshold. BNB Chain documents a finalized JSON-RPC block tag and says fast finality can finalize a block by block n+2 when validator votes are available; if fast finality is unavailable, the chain uses probabilistic finality.

Keep provisional events reversible: if a block is replaced, remove its events and rebuild from the last common canonical block. Wallet displays can show recent activity promptly while marking it pending confirmation.

How can an indexer keep token balances consistent?

Store token metadata separately from transfer events, and treat decimals as display metadata rather than changing raw amounts. ERC-20-compatible tokens report integer values in their smallest units; formatting a balance requires the token’s decimals value.

Make ingestion idempotent by keying events with chain ID, block hash, transaction hash and log index. Persist the event rows and checkpoint together, then replay a range after a restart without duplicating transfers.

• Scope every record to the correct chain and contract.
• Order logs within canonical blocks and check parent hashes.
• Separate provisional activity from finalized history.
• Store raw amounts and make replays idempotent.

These invariants let indexers serve fast wallet views while preserving a route back to canonical chain data. The next step is to test reorg handling, replay and token formatting against real blocks before publishing indexed balances.