SELECT 
  * 
FROM 
  jmj_product_feature_variants 
WHERE 
  variant_id IN (
    3246, 3247, 776, 778, 790, 797, 812, 817, 
    820, 782, 2103, 2107, 2115, 2142, 2148, 
    2169, 2180, 2196, 2228, 2237, 766
  )

Query time 0.00087

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "50.41"
    },
    "table": {
      "table_name": "jmj_product_feature_variants",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "variant_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 21,
      "rows_produced_per_join": 21,
      "filtered": "100.00",
      "index_condition": "(`jmj_test`.`jmj_product_feature_variants`.`variant_id` in (3246,3247,776,778,790,797,812,817,820,782,2103,2107,2115,2142,2148,2169,2180,2196,2228,2237,766))",
      "cost_info": {
        "read_cost": "46.21",
        "eval_cost": "4.20",
        "prefix_cost": "50.41",
        "data_read_per_join": "32K"
      },
      "used_columns": [
        "variant_id",
        "feature_id",
        "url",
        "color",
        "position",
        "abt__ut2_color_style",
        "abt__ut2_multicolor"
      ]
    }
  }
}