title: 'Snapshot Refresh Mode'
sidebar_label: 'Snapshot'
description: 'Reload acceleration data exclusively from the snapshot store.'
sidebar_position: 5
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The snapshot refresh mode creates a read-only acceleration that reloads exclusively from the snapshot store. The federated source is never queried for refreshes — instead, the runtime polls the snapshot store on a configurable interval and atomically swaps in newer snapshots when available.
Use snapshot when:
- A separate writer publishes acceleration snapshots to object storage.
- Read replicas need fast, source-independent startup and refresh.
- The federated source should not be queried by the replica (e.g., edge nodes, security boundaries, or to reduce source load).
Configuration
Requirements
acceleration.snapshots must be enabled or bootstrap_only.- The acceleration engine must be a snapshot-capable file-based engine: DuckDB, SQLite, Cayenne, or Turso.
Behavior
- On startup, the runtime bootstraps from the most recent snapshot, identical to other snapshot-enabled modes.
- After bootstrap, the runtime polls the snapshot store at
refresh_check_interval (default: 60s) for newer snapshots.
- When a newer snapshot is found, its schema is validated against the current acceleration schema before downloading.
- The accelerator file is swapped atomically — queries continue to be served from the previous snapshot until the swap completes.
INSERT INTO statements are rejected with an error since the acceleration is driven exclusively from snapshots.
:::tip
Use refresh_mode: snapshot for read-only replicas that should not access the federated source — for example, edge nodes that receive snapshots from a centralized writer.
:::
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