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Overview

LangChain provides a key-value store interface for storing and retrieving data by key. The key-value store interface in LangChain is primarily used for caching embeddings.

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Interface

All BaseStores are generic and support the following interface, where K represents the key type and V represents the value type:
  • mget(keys: K[]): Promise<(V | undefined)[]>: get the values for multiple keys, returning undefined if a key does not exist
  • mset(keyValuePairs: [K, V][]): Promise<void>: set the values for multiple keys
  • mdelete(keys: K[]): Promise<void>: delete multiple keys
  • yieldKeys(prefix?: string): AsyncGenerator<K | string>: asynchronously yield all keys in the store, optionally filtering by a prefix
The generic nature of the interface allows you to use different types for keys and values. For example, BaseStore<string, BaseMessage> would store messages with string keys, while BaseStore<string, number[]> would store arrays of numbers.
Base stores are designed to work with multiple key-value pairs at once for efficiency. This saves on network round-trips and may allow for more efficient batch operations in the underlying store.

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Built-in stores for local development

InMemoryStore

LocalFileStore

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Custom stores

You can also implement your own custom store by extending the BaseStore class. See the store interface documentation for more details.

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All integrations

Cassandra KV

IORedis

Upstash Redis

Vercel KV

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