Skip to main content
Use this page when the stream definitions are ready and you need to wire the runtime, database, and optional API surface.

​
Architecture

The typical Thru indexing stack looks like this: 
Chain RPC -> @thru/replay ChainClient -> @thru/indexer runtime -> Postgres tables
                                                         \
                                                          -> optional generated Hono routes

​
Tech Stack Assumptions

The current @thru/indexer runtime assumes:
  • PostgreSQL-backed tables generated through Drizzle
  • a Drizzle database client passed as db
  • a clientFactory that returns a ChainClient from @thru/replay
Optional but common:
  • Hono for generated stream routes via mountStreamRoutes(...)
  • Drizzle Kit for migrations
  • a standalone Node service to run the indexer continuously
If you are not using Postgres plus Drizzle, do not start here. Start with the package reference for @thru/indexer and validate whether the current runtime fits your stack.

​
Runtime Setup

import { Indexer } from "@thru/indexer";
import { ChainClient } from "@thru/replay";
import { db } from "./db";
import tokenTransfers from "./streams/token-transfers";
import tokenAccounts from "./account-streams/token-accounts";

export function createIndexer() {
  return new Indexer({
    db,
    clientFactory: () => new ChainClient({ baseUrl: process.env.CHAIN_RPC_URL! }),
    eventStreams: [tokenTransfers],
    accountStreams: [tokenAccounts],
    defaultStartSlot: 0n,
    safetyMargin: 64,
    pageSize: 512,
    logLevel: "info",
  });
}

​
What Each Runtime Option Does

OptionWhat it controls
dbThe Drizzle client used for inserts, updates, checkpoints, and generated route queries.
clientFactoryFresh replay client creation for backfill and live streaming.
eventStreamsAppend-only streams for event rows.
accountStreamsCurrent-state streams for account rows.
defaultStartSlotStarting slot when no checkpoint exists yet.
safetyMarginHow far behind the live tip replay should stay during backfill-to-live switchover.
pageSizeHow many records to request per backfill page.
logLevelRuntime verbosity.

​
Checkpoints And Schema

Your Drizzle schema needs the checkpoint table plus every stream table. 
export { checkpointTable } from "@thru/indexer";
export { tokenTransferEvents } from "./streams/token-transfers";
export { tokenAccountsTable } from "./account-streams/token-accounts";
Without checkpointTable, the runtime cannot resume safely after restarts.

​
Process Shape

In practice, most apps run the indexer as its own long-lived service:
  1. load environment and connect to Postgres
  2. run or verify migrations
  3. build the Indexer
  4. call await indexer.start()
  5. stop gracefully on SIGTERM or SIGINT

​
Generated API Routes

If you want a read API over indexed rows, @thru/indexer can mount generated routes into a Hono app: 
import { OpenAPIHono } from "@hono/zod-openapi";
import { mountStreamRoutes } from "@thru/indexer";
import { db } from "./db";
import tokenTransfers from "./streams/token-transfers";
import tokenAccounts from "./account-streams/token-accounts";

const app = new OpenAPIHono();

mountStreamRoutes(app, {
  db,
  pathPrefix: "/api/v1",
  eventStreams: [tokenTransfers],
  accountStreams: [tokenAccounts],
});
Use that when you want a quick query surface without writing every route by hand.

​
Next Step

Open Querying Indexed Data once rows are landing in Postgres.