Indexing On-chain Data for Small Projects

Almost every crypto app eventually needs to show on-chain data in a friendly way: a user's transaction history, a leaderboard, total deposits, recent sales or a feed of activity. Blockchains store this data, but not in a form that is easy to query. Asking a node for "all deposits by this user in the last month" is slow or impossible without some kind of indexing.

Large protocols run complex data pipelines. Small projects can start much simpler.

What indexing means

Indexing means reading blockchain data, usually events and transactions, and storing it in a database structured for your app's queries. Instead of scanning the chain each time a user loads a page, your app queries the database.

A basic indexer does four things:

1. Fetches new blocks or events from an RPC provider
2. Decodes events into meaningful fields
3. Stores them in a database
4. Serves them through an API or directly to the frontend

Option 1: Query the chain directly

For very small needs, you may not need an indexer at all. If your app only needs recent events for one contract, direct eth_getLogs queries with small block ranges can work. Cache results briefly to avoid repeated calls.

This works when:

• Data volume is low
• Queries cover recent blocks only
• Real-time freshness matters more than history

It breaks down when you need long histories or complex filters.

Option 2: Build a small custom indexer

A simple custom indexer can run as a scheduled serverless function with a small SQL database:

Component	Role
Scheduled job	Runs every minute or few minutes
Cursor table	Stores the last processed block per contract and network
Event fetcher	Queries logs in chunks within provider limits
Decoder	Turns topics and data into columns
Database tables	Store events with indexes on common query fields
API	Serves filtered results to the frontend

Make processing idempotent by using transaction hash and log index as a unique key. That way, reprocessing a block never creates duplicates.

Handle reorgs and confirmations

Only index blocks that have enough confirmations, or mark recent rows as provisional and confirm them later. If you index the chain head, occasional reorganisations can leave incorrect rows. A safe block margin avoids most problems.

Option 3: Use hosted indexing services

Hosted indexers and subgraph platforms let you define which contracts and events to track, then query results through an API. They handle scaling, reorgs and history backfills.

Consider hosted services when:

• You need full historical data from contract deployment
• You track many contracts or networks
• Your team lacks time to maintain infrastructure
• Query patterns are complex

Check pricing, rate limits and data retention before committing, and keep your schema portable in case you need to switch.

Option 4: Analytics platforms

For internal dashboards and one-off analysis, SQL-based blockchain analytics platforms let you query decoded data without running anything yourself. They are excellent for research and public dashboards, though usually not suited as a live backend for your app.

Designing tables well

Good indexing starts with knowing your queries:

• What will users filter by? Address, time, token or event type?
• What sorting do you need? Usually block number or timestamp.
• What aggregates do you show? Totals, counts or leaderboards?

Add database indexes on filtered columns, store amounts as strings or big integers, and keep raw data alongside decoded fields for debugging.

Keep it maintainable

Small indexers fail quietly. Add basic monitoring:

1. Alert when the cursor stops advancing
2. Log RPC errors with context
3. Compare indexed totals with on-chain totals occasionally
4. Document how to backfill after downtime

Start small

Many successful apps began with a single table and a scheduled job. Proud Globe, for example, tracks payment detection progress per order with a simple cursor in one database row, scanning public RPC endpoints in chunks. If you are building your own small data project, a pin on the globe is a quick way to show it to other builders.