How to Build a Blockchain Indexer in Go: Architecture Guide

Frequently Asked Questions

01.What is a blockchain indexer?

A blockchain indexer is a dedicated processing system that reads raw block and transaction data from a node, decodes it into structured records, and writes it into a query-optimized database such as PostgreSQL. It eliminates the need to scan the full chain for every query, reducing typical history lookups from minutes to milliseconds.

02.Why use Go to build a blockchain indexer?

Go's goroutine model allows hundreds of blocks to be fetched and processed concurrently with minimal memory overhead. Its compiled nature, static typing, and first-class channel primitives make it well suited for high-throughput data pipelines. The go-ethereum library provides native Ethereum RPC and WebSocket subscription support without additional dependencies.

03.How do you handle blockchain reorganizations in an indexer?

When a reorg occurs, the canonical chain forks and one or more previously indexed blocks become stale. A production indexer tracks parent block hashes in the database. On each new block, it compares the parent hash against the stored head. If they diverge, it rolls back indexed data to the last common ancestor block before re-indexing the canonical fork.

04.What database should I use for a blockchain indexer?

PostgreSQL is the most common choice for relational queries such as wallet history, token balances, and event joins. For high write throughput on event streams, TimescaleDB (a PostgreSQL extension) adds time-series partitioning. NoSQL stores like MongoDB work well for flexible NFT metadata schemas. The right choice depends on query patterns, not data volume alone.

05.How do you decode Ethereum smart contract events in Go?

Use go-ethereum's accounts/abi package to parse the contract ABI JSON file, then call abi.Unpack or abi.UnpackIntoInterface to decode the topics and data fields of each log. The first topic is always the Keccak-256 hash of the event signature, which you use to filter the correct event type before unpacking the remaining indexed and non-indexed parameters.