Getting Started with Blockchain Indexing
When working with a blockchain, you typically have a node — or a set of nodes — that communicate over a peer-to-peer network. If you want to analyze what’s happening on-chain, you need a way to extract and process blockchain data from these nodes.
There are many kinds of services that depend on blockchain data indexing:
- Analytics systems that scan everything happening on-chain and run machine learning or statistical pipelines on top of that data.
- Targeted indexers that track specific smart contracts, collect event data, and aggregate it for reporting or visualization.
- Reactive services that monitor for particular on-chain events and trigger some action when those events occur.
In all of these cases, the task is the same: retrieve data from the blockchain and make it accessible for further processing.
In this article, we’ll walk through how blockchain indexers evolved — starting with the simplest approach using Ethereum as an example.
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The Most Basic Blockchain Data Indexing Solution
At the core of any blockchain indexing tool is the node. The node exposes an RPC interface, which allows external services to extract data from the blockchain.
On Ethereum, the most basic method is eth_getLogs. Logs are a special type of data structure designed by smart contract developers to emit information for off-chain consumers — precisely for blockchain data indexers.