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

Query time 0.00051

JSON explain

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