Adapters

An adapter is the piece of FastAuth that talks to your database. Providers authenticate users; adapters persist and retrieve them.

The adapter pattern

FastAuth defines adapters as Python Protocol classes. This means you never inherit from a FastAuth base class. You implement the required methods on your own class and pass it in — if the methods match the protocol, it works.

This design lets FastAuth support any database engine without pulling in unwanted dependencies.

Available adapters

SQLAlchemyAdapter

The recommended choice for most applications. Supports any SQLAlchemy-compatible async database:

• SQLite (development) via aiosqlite
• PostgreSQL (production) via asyncpg
• MySQL via aiomysql

SQLAlchemyAdapter is a factory — one object gives you all the sub-adapters:

from fastauth.adapters.sqlalchemy import SQLAlchemyAdapter

adapter = SQLAlchemyAdapter(engine_url="sqlite+aiosqlite:///./auth.db")

config = FastAuthConfig(
    adapter=adapter.user,        # UserAdapter
    token_adapter=adapter.token, # TokenAdapter (email/password reset tokens)
    oauth_adapter=adapter.oauth, # OAuthAccountAdapter (linked social accounts)
    # role_adapter set separately on auth.role_adapter
)

See SQLAlchemy Adapter for the full guide.

MemoryAdapter

An in-memory adapter for testing. No database required.

from fastauth.adapters.memory import MemoryUserAdapter

config = FastAuthConfig(
    adapter=MemoryUserAdapter(),
    ...
)

See Memory Adapter.

Sub-adapter protocols

FastAuth splits storage responsibilities across several protocols:

Protocol	Purpose	Config field
UserAdapter	Create, read, update, delete users	adapter
TokenAdapter	Persist one-time verification/reset tokens	token_adapter
SessionAdapter	Store server-side sessions	used internally
OAuthAccountAdapter	Link OAuth provider accounts to users	oauth_adapter
RoleAdapter	Manage roles and permissions	auth.role_adapter

You only need to configure the protocols relevant to your feature set. Email verification requires a TokenAdapter; OAuth requires an OAuthAccountAdapter; RBAC requires a RoleAdapter.

Custom adapters

If you use a database not supported by SQLAlchemy, or you have existing models, you can implement the protocol directly. See Custom Adapter.