Sandbox

SELECT 
  cscart_cp_popups.* 
FROM 
  cscart_cp_popups 
  LEFT JOIN cscart_cp_popup_links ON cscart_cp_popups.popup_id = cscart_cp_popup_links.popup_id 
  LEFT JOIN cscart_companies ON cscart_companies.company_id = cscart_cp_popups.company_id 
WHERE 
  cscart_cp_popup_links.link_object_id = 906 
  AND cscart_cp_popup_links.link_type = 'P' 
  AND cscart_cp_popups.status = 'A' 
  AND (
    cscart_cp_popups.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_cp_popups.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_cp_popups.usergroup_ids
    )
  ) 
  AND cscart_companies.company_id = 1 
ORDER BY 
  cscart_cp_popups.priority DESC 
limit 
  0, 
  1

Query time 0.00073

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}