memory-layer

A DynamoDB-backed BaseStore for LangGraph — cross-thread memory for your agents without standing up Postgres/pgvector.

LangGraph's checkpointer persists state inside a thread — when a user opens a new conversation, the graph starts from zero. The store protocol is LangGraph's answer to that: memory that survives across threads, shared by every session for the same user (or the same tenant). LangGraph ships an official store for Postgres. If your stack is already DynamoDB — which a lot of serverless/Fargate deployments are — there wasn't an official option. memory-layer is that option.

from memory_layer import DynamoDBStore

store = DynamoDBStore(table_name="my-app-memories")
graph = builder.compile(checkpointer=checkpointer, store=store)

That's the whole integration. No new infra beyond one DynamoDB table you probably already know how to provision.

Why this exists

• You're already on DynamoDB. Adding Postgres + pgvector just for agent memory is a real infra cost — a new engine, a new backup story, a new thing to monitor — for a feature that, for most products, doesn't need vector search on day one.
• LangGraph's store protocol is a clean seam. It's designed so storage is swappable — your agent code shouldn't care whether memories live in Postgres, Dynamo, or Redis. This fills the Dynamo gap in that seam.
• Memory doesn't have to mean embeddings. Most products get real value from "the last N things we know about this user," fetched by recency — no vector index required. memory-layer starts there, and gives you a clean place to add semantic ranking later if you actually need it.

Features

• DynamoDBStore — a complete langgraph.store.base.BaseStore implementation: get/put/search (and their async counterparts), real pagination via DynamoDB's LastEvaluatedKey (not a "hope the first page has enough" heuristic), per-item filtering, and per-type TTL (e.g. auto-expire episodic memories after 90 days while semantic ones never expire).
• SimpleRetrieval — fetch a user's N most recent memories and turn them into a ready-to-inject prompt block. No embeddings, no extra dependencies.
• MemoryWriter — an LLM-driven extraction step: hand it a conversation, it classifies and persists the facts worth remembering, via with_structured_output (a real schema-validated response, not a hand-rolled JSON parser hoping the model didn't wrap the array in a sentence).
• Scopes, not just users. Namespaces are plain tuples (("user", user_id), ("instance", tenant_id)) — model per-user memory, per-tenant shared context, or your own scope, however your product actually shapes ownership.

Install

pip install langgraph-dynamodb-store

Want LLM-driven extraction? MemoryWriter takes any LangChain BaseChatModel — bring the one you already use, no extra install needed. numpy/langchain-openai are only required for the semantic-retrieval extra (see Roadmap):

pip install "langgraph-dynamodb-store[semantic]"

DynamoDB table

One table, no secondary index needed — search() queries the base table directly using begins_with on a composite sort key, so a namespace prefix like ("user", "123") correctly matches everything stored under it (including deeper namespaces like ("user", "123", "preferences")), not just an exact match. Create it however you provision infra (CDK/Terraform/console) — here's the raw shape via the AWS CLI, if you just want to try it out:

aws dynamodb create-table \
  --table-name my-app-memories \
  --attribute-definitions \
      AttributeName=owner_id,AttributeType=S \
      AttributeName=sort_key,AttributeType=S \
  --key-schema \
      AttributeName=owner_id,KeyType=HASH \
      AttributeName=sort_key,KeyType=RANGE \
  --billing-mode PAY_PER_REQUEST

# Optional but recommended — lets episodic memories actually expire instead of
# accumulating forever. memory-layer sets the `ttl` attribute; DynamoDB does the rest.
aws dynamodb update-time-to-live \
  --table-name my-app-memories \
  --time-to-live-specification "Enabled=true, AttributeName=ttl"

Set MEMORY_TABLE=my-app-memories or pass table_name explicitly — DynamoDBStore(table_name="my-app-memories").

Quickstart

from memory_layer import DynamoDBStore

store = DynamoDBStore(table_name="my-app-memories")

namespace = ("user", "user-123")

store.put(namespace, "mem-1", {"content": "Prefers responses in Spanish", "type": "semantic"})
store.put(namespace, "mem-2", {"content": "Reviewed Q3 numbers on 2026-08-01", "type": "episodic"})

memories = store.search(namespace, limit=10)
for m in memories:
    print(m.value["content"])

Inside a LangGraph node

LangGraph injects store into any node whose signature asks for it:

from langgraph.store.base import BaseStore
from langchain_core.runnables import RunnableConfig

from memory_layer import DynamoDBStore
from memory_layer.retrieval import SimpleRetrieval

store = DynamoDBStore(table_name="my-app-memories")
graph = builder.compile(checkpointer=checkpointer, store=store)

def supervisor_node(state: AgentState, config: RunnableConfig, store: BaseStore) -> dict:
    user_id = state["context"]["user_id"]
    retrieval = SimpleRetrieval(store, limit=5)
    memories = retrieval.fetch(("user", user_id))
    memory_block = retrieval.to_prompt_block(memories)
    # ...inject memory_block into the system prompt
    return {}

Writing memories back

from memory_layer.writer import MemoryWriter

writer = MemoryWriter(llm=your_chat_model, store=store)

async def memory_writer_node(state: AgentState) -> dict:
    await writer.extract_and_save(
        namespace=("user", state["context"]["user_id"]),
        messages=state["messages"],
        session_id=state["context"]["session_id"],
    )
    return {}

The extraction LLM only needs with_structured_output support — every major provider's LangChain integration has it.

Memory types

TTL policy per type lives in memory_layer.store._TTL_SECONDS_BY_TYPE — override it if 90 days isn't the right default for your product.

Scopes

A namespace is just a tuple — memory-layer doesn't prescribe what it means, but the common shapes are:

("user", cognito_sub)        # private to one user
("instance", tenant_id)      # shared across every user of one tenant

Roadmap

• Semantic retrieval — embed memories + query, rank by cosine similarity, for products that outgrow "most recent N" (roughly ~20+ memories per user is where this starts to matter). Lives behind the semantic extra so the core library stays dependency-light.
• Deduplication on write — skip persisting a fact that's a near-duplicate of one already stored.
• Bring-your-own embeddings backend — DynamoDB-native cosine similarity to start; pluggable enough to swap in pgvector/a real vector store later if volume ever justifies it.

Development

pip install -e ".[dev]"
pytest

Tests run against moto — no real AWS account or network access required.

License

MIT — see LICENSE.