dynamoxy

A typed, async DynamoDB ORM for Python, with a Rust core. Declare models with type hints (or pydantic) and get validated, atomic DynamoDB access, plus an in-memory DynamoDB for your tests.

import asyncio
from datetime import datetime

import dynamoxy
from dynamoxy import Attr, field, partition_key


class User(dynamoxy.Model, table="users"):
    user_id: Attr[str] = partition_key()
    email: Attr[str] = field(unique=True)
    name: Attr[str] = field(min_length=1)
    visits: Attr[int] = field(default=0)
    created_at: Attr[datetime] = dynamoxy.created_at()
    version: Attr[int] = dynamoxy.version()

    by_email = dynamoxy.GlobalIndex(partition_key=email)


async def main() -> None:
    async with dynamoxy.Client(region="eu-west-1") as client:  # or dynamoxy.testing.memory_client()
        await client.ensure_tables(User)
        users = client.repository(User)

        ada = await users.create(User(user_id="u1", email="ada@example.com", name="Ada"))
        await ada.increment(User.visits)  # atomic; `ada` is refreshed in place
        ada.name = "Ada Lovelace"
        await ada.save()  # only if nobody changed it meanwhile (version)

        try:
            await users.create(User(user_id="u2", email="ada@example.com", name="Imposter"))
        except dynamoxy.UniqueConstraintError as error:
            print(f"{error.field} is taken")

        found = await users.query(index=User.by_email, email="ada@example.com").first()
        print(found)


asyncio.run(main())

Highlights

• Typed end to end. Fields are values on instances and typed paths on the class (User.visits > 3). Your type checker catches User(visits="3") and User.visits > "3".

• Errors that tell you what to fix. DynamoDB's rules are checked before a request is sent:

  ValidationError: the transaction has 120 operations (guard items of unique attributes included); DynamoDB allows 100
  

  A refused write raises ItemAlreadyExistsError, VersionConflictError or UniqueConstraintError, not a bare ConditionalCheckFailedException.

• Writes that mean what they say. create() never overwrites, save() checks the version, update() is atomic without a read.

• Unique values, timestamps and versions are maintained for you.

• Retries built in, with backoff and jitter. Nothing fails silently.

• An in-memory DynamoDB for tests. No Docker, no AWS account. It refuses what DynamoDB refuses, simulates faults and answers in microseconds:

  dynamoxy.testing.inject_fault(client, operation="GetItem", error="throttling", times=2)
  with dynamoxy.collect() as usage:
      user = await users.get("u1")  # throttled twice, retried
  assert usage.retries == 2
  

• Observable. Structured logs and event hooks out of the box; OpenTelemetry spans and metrics when you configure it. Item contents are never logged.

• Single-table design with key templates such as "CUSTOMER#{customer_id}".

• Fast. 2.5 to 5 times less client CPU per call than boto3 (numbers).

• No required dependencies. pydantic and OpenTelemetry are optional extras.

Also covered: indexes, cursors, batches, transactions, TTL, streams, backups, PartiQL and table management.

Already using pydantic?

Inherit from dynamoxy.PydanticModel instead of BaseModel and mark the key. Pydantic keeps validating, and the class stays a pydantic model, so the same Customer can be a FastAPI request or response model and a DynamoDB table (uv add 'dynamoxy[pydantic]'):

from typing import Annotated

from pydantic import BaseModel, Field

import dynamoxy


class Address(BaseModel):  # plain pydantic models nest as maps
    street: str
    city: str


class Customer(dynamoxy.PydanticModel, table="customers"):  # instead of BaseModel
    customer_id: Annotated[str, dynamoxy.PartitionKey()]
    email: Annotated[str, dynamoxy.Unique()]
    name: str = Field(min_length=1)
    address: Address | None = None


await client.ensure_tables(Customer)
customers = client.repository(Customer)
await customers.create(Customer(customer_id="c1", email="ada@example.com", name="Ada"))
customer = await customers.get("c1")  # a validated Customer

A model you would rather not touch can stay as it is: subclass it together with dynamoxy.PydanticModel and re-declare only the fields that need a marker, such as the key (see the pydantic guide).

Install

uv add dynamoxy               # or: pip install dynamoxy
uv add 'dynamoxy[pydantic]'   # pydantic models
uv add 'dynamoxy[otel]'       # OpenTelemetry

Documentation

AI agents: run dynamoxy guide (or read AGENT_GUIDE.md) before writing code with dynamoxy; application repositories can copy the skill in skills/dynamoxy. Agents changing dynamoxy itself start with AGENTS.md.

How it works

A Rust core speaks DynamoDB: the AWS SDK for transport, plus dynamoxy's own retries, batching, events and the in-memory backend. Python owns what you touch: models, validation, repositories and hooks. A few choices worth knowing:

• Values never go into expression strings, so reserved words and injection are non-issues.
• Unique values are guard items written in the same transaction, since indexes are only eventually consistent.
• Models hold no client, so one model works with several accounts, regions or test stores.
• Stored formats are API: they stay readable across versions.

The architecture and the decision records have the details.

Performance

Round trips cost every client the same. What a library adds is CPU time per call, spent holding the GIL. dynamoxy does the protocol work in Rust.

Client CPU time per call against a local emulator (dynamoxy returns validated models; the others return DynamoDB JSON):

• Cold start (import and first read): 51 ms, against 115 ms for boto3.
• In memory, a get() takes about 13 µs, so large test suites run in seconds.

Why it is fast: signing, HTTP, JSON and retries run in Rust outside the GIL; each model plans its encoding once, when the class is created; and features you do not use cost nothing.

Measured with dynamoxy 0.2.0 on Python 3.14, aarch64 Linux, October 2026. Your hardware will differ: scripts/benchmark.py measures it on yours.

Contributing

See CONTRIBUTING.md. The project is young (0.x): breaking changes are possible in minor versions and are called out in the changelog.

License

MIT