SELECT 
  `variant_id`, 
  `variant` 
FROM 
  cscart_product_feature_variant_descriptions 
WHERE 
  `link` = 'hash=737-%5B373%2C373%5D&variant=373'

Query time 0.00269

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "615.80"
    },
    "table": {
      "table_name": "cscart_product_feature_variant_descriptions",
      "access_type": "ALL",
      "rows_examined_per_scan": 6103,
      "rows_produced_per_join": 610,
      "filtered": "10.00",
      "cost_info": {
        "read_cost": "554.77",
        "eval_cost": "61.03",
        "prefix_cost": "615.80",
        "data_read_per_join": "2M"
      },
      "used_columns": [
        "variant_id",
        "variant",
        "link"
      ],
      "attached_condition": "(`dev2`.`cscart_product_feature_variant_descriptions`.`link` = 'hash=737-%5B373%2C373%5D&variant=373')"
    }
  }
}