SQLAlchemy 2.0 select with filters and efficient pagination

from sqlalchemy import select, func
from sqlalchemy.orm import selectinload
import math

async def list_traces(
    session: AsyncSession,
    status: str | None = None,
    tag: str | None = None,
    page: int = 1,
    page_size: int = 20,
) -> tuple[list[Trace], int]:
    base_q = select(Trace).options(selectinload(Trace.tags))

    if status:
        base_q = base_q.where(Trace.status == status)
    if tag:
        base_q = base_q.where(Trace.tags.any(Tag.name == normalize_tag(tag)))

    # Count without limit:
    total = (await session.execute(
        select(func.count()).select_from(base_q.subquery())
    )).scalar_one()

    # Paginated results:
    offset = (page - 1) * page_size
    result = await session.execute(
        base_q.order_by(Trace.created_at.desc())
              .offset(offset).limit(page_size)
    )
    return result.scalars().unique().all(), total

@router.get('/traces')
async def list_endpoint(page: int = 1, page_size: int = Query(20, le=100)):
    traces, total = await list_traces(db, page=page, page_size=page_size)
    return {
        'items': traces,
        'total': total,
        'page': page,
        'pages': math.ceil(total / page_size),
    }