SELECT 
  cscart_users.* 
FROM 
  cscart_users 
WHERE 
  user_id = 70548

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.00"
    },
    "table": {
      "table_name": "cscart_users",
      "access_type": "const",
      "possible_keys": [
        "PRIMARY"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "user_id"
      ],
      "key_length": "3",
      "ref": [
        "const"
      ],
      "rows_examined_per_scan": 1,
      "rows_produced_per_join": 1,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "0.00",
        "eval_cost": "0.10",
        "prefix_cost": "0.00",
        "data_read_per_join": "6K"
      },
      "used_columns": [
        "user_id",
        "status",
        "brand_id",
        "user_type",
        "user_login",
        "referer",
        "is_root",
        "company_id",
        "last_login",
        "timestamp",
        "password",
        "salt",
        "firstname",
        "lastname",
        "company",
        "email",
        "phone",
        "fax",
        "url",
        "tax_exempt",
        "lang_code",
        "birthday",
        "purchase_timestamp_from",
        "purchase_timestamp_to",
        "responsible_email",
        "password_change_timestamp",
        "api_key",
        "janrain_identifier",
        "partner_id",
        "last_activity",
        "helpdesk_user_id",
        "is_primary_account",
        "instagram_handle",
        "cp_phone_verified"
      ]
    }
  }
}