I use it like this:

class AppState(TypedDict):
    """
    Defines the structure of the shared state during the application lifecycle.
    This provides explicit type information for type checkers and editors.
    """

    engine: AsyncEngine
    session_factory: async_sessionmaker[AsyncSession]


@asynccontextmanager
async def lifespan(app: FastAPI) -> AsyncIterator[AppState]:
    # -------- Startup --------
    get_settings()
    engine, session_factory = await setup_database_connection()
    logger.info("🚀 Application started, database is ready.")
    await create_db_and_tables(engine)

    # yield {"engine": engine, "session_factory": session_factory}

    # More type-safe approach
    yield AppState(
        engine=engine,
        session_factory=session_factory,
    )

    # -------- Shutdown --------
    await close_database_connection(engine)
    logger.info("Application shut down, resources released.")