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PostgreSQL

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The Postgres backend provides all three persistence components against a single PostgreSQL database, via the pg driver:

  • PostgresJournal — the event journal for PersistentActors.
  • PostgresSnapshotStore — snapshots to bound recovery.
  • PostgresDurableStateStore — key-value durable state for DurableStateActors. This is the first SQL-backed durable-state store (SQLite and Cassandra ship journal + snapshot only).

Like Cassandra, Postgres is shared across cluster nodes — any node can read or write any persistenceId — but it’s relational, transactional, and almost certainly already in your stack.

Install

Section titled “Install”

pg is an optional peer dependency — install it alongside actor-ts:

Terminal window
bun add pg

The framework lazy-imports pg only when a Postgres store is first used, so it stays out of your bundle until you opt in.

Setup

Section titled “Setup”

Register the journal + snapshot store against the PersistenceExtension and receive a ready-to-use durable-state store. Pass a shared pool so all three components reuse one connection pool:

import { Pool } from 'pg';
import {
  ActorSystem,
  PersistenceExtensionId,
  registerPostgresPlugins,
} from 'actor-ts';


const system = new ActorSystem({
  name: 'my-app',
  // Select the Postgres plugins as the active journal + snapshot store.
  config: `
    actor-ts.persistence.journal.plugin = "actor-ts.persistence.journal.postgres"
    actor-ts.persistence.snapshot-store.plugin = "actor-ts.persistence.snapshot-store.postgres"
  `,
});


const ext = system.extension(PersistenceExtensionId);
const { durableStateStore } = registerPostgresPlugins(ext, {
  // One pool shared by journal + snapshot + durable-state (recommended).
  pool: new Pool({ connectionString: 'postgres://user:pass@host:5432/app' }),
  journal:           { /* eventsTable, tagsTable, autoCreateTables */ },
  snapshotStore:     { keepN: 3 },
  durableStateStore: { /* table */ },
});

registerPostgresPlugins registers the journal + snapshot store via the extension (selected by the config plugin IDs above) and returns the durable-state store. PersistenceExtension has no durable-state registry — hand durableStateStore to your DurableStateActor settings directly (same pattern as the object-storage plugin).

Without a shared pool, each component lazily builds its own pool from its url / poolConfig:

registerPostgresPlugins(ext, {
  journal:           { url: 'postgres://user:pass@host:5432/app' },
  snapshotStore:     { url: 'postgres://user:pass@host:5432/app', keepN: 3 },
  durableStateStore: { url: 'postgres://user:pass@host:5432/app' },
});

When to use it

Section titled “When to use it”
  • You already run Postgres. One less moving part than standing up Cassandra — reuse your existing managed instance (RDS, Cloud SQL, Supabase, …).
  • Cluster-shared persistence. Sharded entities that move between nodes, or cross-node projections, need a journal every node can read.
  • You want durable state in SQL. The only SQL durable-state store in the framework.

For single-node dev, SqliteJournal is simpler (one file, no server).

Configuration

Section titled “Configuration”
interface PostgresConnection {
  url?:        string;                      // postgres://user:pass@host:5432/db
  poolConfig?: Record<string, unknown>;     // extra pg.Pool config (ssl, max, …)
  pool?:       PgPoolLike;                   // pre-built / shared pool
}


interface PostgresJournalOptions extends PostgresConnection {
  eventsTable?:      string;   // default 'events'
  tagsTable?:        string;   // default '<eventsTable>_tags'
  autoCreateTables?: boolean;  // default true
}
interface PostgresSnapshotStoreOptions extends PostgresConnection {
  snapshotsTable?:   string;   // default 'snapshots'
  keepN?:            number;   // keep newest N per pid; default 3, <=0 keeps all
  autoCreateTables?: boolean;
}
interface PostgresDurableStateStoreOptions extends PostgresConnection {
  table?:            string;   // default 'durable_state'
  autoCreateTables?: boolean;
}

Table names come from config (not user input) and are validated against a safe-identifier pattern; everything else — persistenceIds, tags, payloads — is passed as bind parameters ($1, $2, …), never string-concatenated.

Schema

Section titled “Schema”

With autoCreateTables (the default), the backend runs CREATE TABLE IF NOT EXISTS on first use:

CREATE TABLE events (
  persistence_id TEXT NOT NULL,
  sequence_nr    BIGINT NOT NULL,
  payload        TEXT NOT NULL,    -- JSON
  tags           TEXT,             -- CSV (also mirrored into events_tags)
  timestamp      BIGINT NOT NULL,
  PRIMARY KEY (persistence_id, sequence_nr)
);
CREATE TABLE events_tags (         -- indexed tag lookups for projections
  persistence_id TEXT NOT NULL,
  sequence_nr    BIGINT NOT NULL,
  tag            TEXT NOT NULL,
  timestamp      BIGINT NOT NULL,
  PRIMARY KEY (tag, timestamp, persistence_id, sequence_nr)
);
CREATE TABLE snapshots (
  persistence_id TEXT NOT NULL,
  sequence_nr    BIGINT NOT NULL,
  payload        TEXT NOT NULL,
  timestamp      BIGINT NOT NULL,
  PRIMARY KEY (persistence_id, sequence_nr)
);
CREATE TABLE durable_state (
  persistence_id TEXT PRIMARY KEY,
  revision       BIGINT NOT NULL,
  payload        TEXT NOT NULL,
  timestamp      BIGINT NOT NULL
);

Pre-provision these (and grant only INSERT/SELECT/UPDATE/DELETE) and set autoCreateTables: false if your DB role can’t run DDL.

Concurrency model

Section titled “Concurrency model”
  • Journal append runs SELECT MAX(sequence_nr) and the inserts inside one transaction; the caller’s expectedSeq is checked against the current head. A racing writer that slips through trips the primary-key unique constraint (SQLSTATE 23505), which is translated to JournalConcurrencyError as a backstop.
  • Durable-state CAS uses the revision column: a create (expectedRevision === 0) is INSERT … ON CONFLICT DO NOTHING, and an update is UPDATE … WHERE revision = expected. Zero rows affected ⇒ DurableStateConcurrencyError, with the current revision read back for the caller.

BIGINT columns come back from pg as strings; the backend coerces sequence_nr / revision / timestamp to number at the mapping boundary.

Pitfalls

Section titled “Pitfalls”

Where to next

Section titled “Where to next”