> ## Documentation Index
> Fetch the complete documentation index at: https://langchain-5e9cc07a-preview-stream-1765228345-2909855.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Key-value stores

## 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](/oss/python/integrations/text_embedding).

## Interface

All [`BaseStores`](https://python.langchain.com/api_reference/core/stores/langchain_core.stores.BaseStore.html) support the following interface:

* `mget(key: Sequence[str]) -> List[Optional[bytes]]`: get the contents of multiple keys, returning `None` if the key does not exist
* `mset(key_value_pairs: Sequence[Tuple[str, bytes]]) -> None`: set the contents of multiple keys
* `mdelete(key: Sequence[str]) -> None`: delete multiple keys
* `yield_keys(prefix: Optional[str] = None) -> Iterator[str]`: yield all keys in the store, optionally filtering by a prefix

<Note>
  Base stores are designed to work **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.
</Note>

## Built-in stores for local development

<Columns cols={2}>
  <Card title="InMemoryByteStore" icon="link" href="/oss/python/integrations/stores/in_memory" arrow="true" cta="View guide" />

  <Card title="LocalFileStore" icon="link" href="/oss/python/integrations/stores/file_system" arrow="true" cta="View guide" />
</Columns>

## Custom stores

You can also implement your own custom store by extending the [`BaseStore`](https://reference.langchain.com/python/langgraph/store/#langgraph.store.base.BaseStore) class. See the [store interface documentation](https://python.langchain.com/api_reference/core/stores/langchain_core.stores.BaseStore.html) for more details.

## All key-value stores

<Columns cols={3}>
  <Card title="AstraDBByteStore" icon="link" href="/oss/python/integrations/stores/astradb" arrow="true" cta="View guide" />

  <Card title="CassandraByteStore" icon="link" href="/oss/python/integrations/stores/cassandra" arrow="true" cta="View guide" />

  <Card title="ElasticsearchEmbeddingsCache" icon="link" href="/oss/python/integrations/stores/elasticsearch" arrow="true" cta="View guide" />

  <Card title="RedisStore" icon="link" href="/oss/python/integrations/stores/redis" arrow="true" cta="View guide" />

  <Card title="UpstashRedisByteStore" icon="link" href="/oss/python/integrations/stores/upstash_redis" arrow="true" cta="View guide" />
</Columns>

***

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