Postgres backend¶

PostgresStore persists state to a PostgreSQL table with the same interface as the in-memory Store. Values are stored as msgpack bytes (the same wire format as the Rust core), so state is durable, shared across processes and machines, and readable by any msgpack consumer.

pip install "swarmstate[postgres]"
# or: uv add "swarmstate[postgres]"

Use it like a `Store`¶

from swarmstate.backends.postgres import PostgresStore

store = PostgresStore("postgresql://user:pass@host:5432/db")
store.set("workflow", "onboarding", {"step": 3})
store.get("workflow", "onboarding")     # -> {"step": 3}

It implements the full interface (set, get, contains, delete, keys, namespaces, clear, len(store), snapshot() / restore()), plus close().

Durable, shared LangGraph checkpoints¶

PostgresStore drops straight into SwarmStateSaver, so LangGraph checkpoints live in your existing Postgres, survive restarts, and are shared across workers:

from swarmstate.backends.postgres import PostgresStore
from swarmstate.integrations.langgraph import SwarmStateSaver

saver = SwarmStateSaver(PostgresStore("postgresql://user:pass@host/db"))
graph = builder.compile(checkpointer=saver)

Which backend?¶

Backend	Persistent	Shared across processes	Needs a server
`Store` (memory)	no	no	no
`DiskStore` (SQLite)	yes (a file)	one machine	no
`RedisStore`	yes	yes (networked)	yes (Redis)
`PostgresStore`	yes	yes (networked)	yes (Postgres)

Connections¶

Connections come from a psycopg_pool pool (max_size=8 by default), so concurrent workers are not serialized through one connection — which is the point of choosing Postgres in the first place:

store = PostgresStore("postgresql://user:pass@host/db", max_size=16)
store = PostgresStore(conn=my_connection)   # opt out: single connection, mutex-guarded

An install without psycopg_pool falls back to the single-connection path automatically. Like DiskStore, max_key is answered from the primary-key index, so the LangGraph saver resolves "newest checkpoint" with an indexed query and writes no pointer row.

Layout & parameters¶

A single table (ns text, k text, v bytea, primary key (ns, k)) (default name swarmstate_kv); v is msgpack bytes.

Parameter	Default	Description
`dsn`	`postgresql:///swarmstate`	libpq connection string
`conn`	`None`	pass an existing `psycopg` connection instead of a DSN
`table`	`"swarmstate_kv"`	table name (validated identifier)
`codec`	`"msgpack"`	value serialization (stable, cross-language)