Persistence

Session-lifecycle state is persisted to a store between requests. Swapping stores is an infrastructure change — your machines and templates never know.

The Store interface

Any store implements four methods over opaque JSON snapshots:

interface Store {
  get(sessionId: string, machineName: string): Promise<unknown | null>
  set(sessionId: string, machineName: string, snapshot: unknown, ttlSeconds: number): Promise<void>
  has(sessionId: string, machineName: string): Promise<boolean>
  deleteSession(sessionId: string): Promise<void>
}

TTL is per session, not per machine — a whole session expires together, so a cart never loses individual lines mid-checkout.

In-memory (default)

InMemoryStore keeps snapshots in a Map. Zero-config and ideal for development, but state is lost on restart — not for production.

store: new InMemoryStore()

Redis

RedisStore persists to Redis so state survives restarts and deploys:

store: new RedisStore(process.env.REDIS_URL)

Cached Redis

CachedStore fronts any store with an in-memory cache (write-through), cutting Redis command counts on chatty sessions:

store: new CachedStore(new RedisStore(url), {
  memoryTtlSeconds: 300,
  maxEntries: 10_000,
})

A crash loses only the cache, not committed state.

What persists

Only lifecycle: 'session' machines are stored. App machines live in process memory and re-seed on boot — see Sessions and state.