SELECT 
  * 
FROM 
  cscart_product_feature_variants 
WHERE 
  variant_id IN (
    178, 399, 410, 412, 149, 50, 58, 147, 201, 
    170, 165, 400, 411, 404, 406
  )

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "10.51"
    },
    "table": {
      "table_name": "cscart_product_feature_variants",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "variant_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 15,
      "rows_produced_per_join": 15,
      "filtered": "100.00",
      "index_condition": "(`test_uchur_k`.`cscart_product_feature_variants`.`variant_id` in (178,399,410,412,149,50,58,147,201,170,165,400,411,404,406))",
      "cost_info": {
        "read_cost": "9.01",
        "eval_cost": "1.50",
        "prefix_cost": "10.51",
        "data_read_per_join": "23K"
      },
      "used_columns": [
        "variant_id",
        "feature_id",
        "url",
        "color",
        "position",
        "abt__ut2_color_style",
        "abt__ut2_multicolor"
      ]
    }
  }
}