deno_kv

This crate provides a key/value store for Deno. For an overview of Deno KV, please read the manual.

Storage Backends

Deno KV has a pluggable storage interface that supports multiple backends:

• SQLite - backed by a local SQLite database. This backend is suitable for development and is the default when running locally.
• Remote - backed by a remote service that implements the KV Connect protocol, for example Deno Deploy.

Additional backends can be added by implementing the DatabaseHandler trait.

KV Connect

The KV Connect protocol has separate control and data planes to maximize throughput and minimize latency. Metadata Exchange and Data Path are the two sub-protocols that are used when talking to a KV Connect-compatible service.

Metadata Exchange

To connect to a KV Connect service, the user provides an HTTP or HTTPS URL to Deno.openKv. A background task is then spawned to periodically make HTTP POST requests to the provided URL to refresh database metadata.

The HTTP Authorization header is included and have the format Bearer <access-token>. The <access-token> is a static token issued by the service provider. For Deno Deploy, this is the personal access token generated from the dashboard. You can specify the access token with the environment variable DENO_KV_ACCESS_TOKEN.

Request body is currently unused. The response is a JSON message that satisfies the JSON Schema definition in cli/schemas/kv-metadata-exchange-response.v1.json.

Semantics of the response fields:

• version: Protocol version. The only supported value is 1.
• databaseId: UUID of the database.
• endpoints: Data plane endpoints that can serve requests to the database, along with their consistency levels.
• token: An ephemeral authentication token that must be included in all requests to the data plane. This value is an opaque string and the client should not depend on its format.
• expiresAt: The time at which the token expires. Encoded as an ISO 8601 string.

Data Path

After the first metadata exchange has completed, the client can talk to the data plane endpoints listed in the endpoints field using a Protobuf-over-HTTP protocol called the Data Path. The Protobuf messages are defined in proto/datapath.proto.

Two sub-endpoints are available under a data plane endpoint URL:

• POST /snapshot_read: Used for read operations: kv.get() and kv.getMany().
  • Request type: SnapshotRead
  • Response type: SnapshotReadOutput
• POST /atomic_write: Used for write operations: kv.set() and kv.atomic().commit().
  • Request type: AtomicWrite
  • Response type: AtomicWriteOutput

An HTTP Authorization header in the format Bearer <ephemeral-token> must be included in all requests to the data plane. The value of <ephemeral-token> is the token field from the metadata exchange response.

Error handling

All non-client errors (i.e. network errors and HTTP 5xx status codes) are handled by retrying the request. Randomized exponential backoff is applied to each retry.

Client errors cannot be recovered by retrying. A JavaScript exception is generated for each of those errors.