SELECT 
  status 
FROM 
  cscart_sg_groups_member 
where 
  user_id = 0 
  and group_id = 1

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}