SELECT 
  * 
FROM 
  cscart_product_feature_variants 
WHERE 
  variant_id IN (
    1, 125, 456, 326, 1333, 1394, 122, 240, 
    121, 127, 1349, 120, 123, 152, 234, 146, 
    50, 57, 58, 147, 6, 111, 238, 165
  )

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.81"
    },
    "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": 24,
      "rows_produced_per_join": 24,
      "filtered": "100.00",
      "index_condition": "(`test_uchur_k`.`cscart_product_feature_variants`.`variant_id` in (1,125,456,326,1333,1394,122,240,121,127,1349,120,123,152,234,146,50,57,58,147,6,111,238,165))",
      "cost_info": {
        "read_cost": "14.41",
        "eval_cost": "2.40",
        "prefix_cost": "16.81",
        "data_read_per_join": "37K"
      },
      "used_columns": [
        "variant_id",
        "feature_id",
        "url",
        "color",
        "position",
        "abt__ut2_color_style",
        "abt__ut2_multicolor"
      ]
    }
  }
}