select 'seen_1h' as metric, count(*)::text as value from cars where last_seen_at >= now() - interval '1 hour'
union all
select 'seen_24h', count(*)::text from cars where last_seen_at >= now() - interval '24 hours'
union all
select 'old_rows_touched_24h', count(*)::text from cars where last_seen_at >= now() - interval '24 hours' and id <= (select greatest(max(id) - 5000, 0) from cars)
union all
select 'min_recent_id_1h', coalesce(min(id)::text, 'null') from cars where last_seen_at >= now() - interval '1 hour'
union all
select 'max_recent_id_1h', coalesce(max(id)::text, 'null') from cars where last_seen_at >= now() - interval '1 hour'
union all
select 'top_5_recent_old_ids_24h', coalesce(string_agg(id::text, ', ' order by last_seen_at desc), 'none')
from (
    select id, last_seen_at
    from cars
    where last_seen_at >= now() - interval '24 hours'
      and id <= (select greatest(max(id) - 5000, 0) from cars)
    order by last_seen_at desc
    limit 5
) t;