I recently published a manifesto and code snippets for exactly this in Postgres!

  delete from task
  where task_id in
  ( select task_id
    from task
    order by random() -- use tablesample for better performance
    for update
    skip locked
    limit 1
  )
  returning task_id, task_type, params::jsonb as params

[1] https://taylor.town/pg-task