SELECT 
  company_ids 
FROM 
  cscart_ec_hb_vendor_favts 
WHERE 
  user_id = 0

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.80"
    },
    "table": {
      "table_name": "cscart_ec_hb_vendor_favts",
      "access_type": "ALL",
      "rows_examined_per_scan": 4,
      "rows_produced_per_join": 1,
      "filtered": "25.00",
      "cost_info": {
        "read_cost": "1.60",
        "eval_cost": "0.20",
        "prefix_cost": "1.80",
        "data_read_per_join": "40"
      },
      "used_columns": [
        "user_id",
        "company_ids"
      ],
      "attached_condition": "(`atulecarter_march_setup`.`cscart_ec_hb_vendor_favts`.`user_id` = 0)"
    }
  }
}