Kysely

@postel/kysely is an ORM/query-builder adapter: you hand Postel the Kysely instance you already use, and it issues its queries (and transactions) through it. That means an outbox insert shares your connection and composes with your own writes — no second pool.

pnpm add @postel/kysely kysely

npm install @postel/kysely kysely

yarn add @postel/kysely kysely

bun add @postel/kysely kysely

Plus your database driver — pg, mysql2, or better-sqlite3.

import { Kysely, PostgresDialect } from "kysely";
import { Pool } from "pg";
import { Postel } from "@postel/core";
import { KyselyStorage } from "@postel/kysely";
import { config } from "./config.js";

const db = new Kysely<DB>({
  dialect: new PostgresDialect({
    pool: new Pool({ connectionString: config.databaseUrl }),
  }),
});

export const postel = Postel({
  outbound: {
    storage: KyselyStorage({ db, dialect: "postgres" }),
  },
});

Options

kysely is a peer dependency. Postel runs through Kysely's sql tag, so your Kysely<DB> needs no Postel-specific table typing. The dialect names a SQL family, so wire-compatible engines (MariaDB, PlanetScale, libSQL/Turso, …) work via the matching dialect — see compatible databases.

On MySQL, build your Kysely instance with a callback-style mysql2 pool — import { createPool } from "mysql2", as Kysely's MysqlDialect documents. A mysql2/promise pool leaves Kysely's getConnection/end callbacks unfired, so every query hangs; this is a Kysely requirement, not Postel-specific.

Shared transactions

Open a Kysely transaction and pass it to send() — the outbox insert commits atomically with your business writes:

await db.transaction().execute(async (trx) => {
  await trx.insertInto("orders").values({ /* ... */ }).execute();
  await postel.send({ type: "order.created", data: { /* ... */ } }, { tx: trx });
});

Migrations

autoMigrate (default true) runs the canonical migrations through your connection, version-gated and idempotent — or run your own tooling against that schema.