SELECT 
  pfv.variant_id, 
  pfv.position, 
  pfvd.variant 
FROM 
  cscart_product_feature_variants AS pfv 
  INNER JOIN cscart_product_feature_variant_descriptions AS pfvd ON pfv.variant_id = pfvd.variant_id 
  AND pfvd.lang_code = 'en' 
WHERE 
  pfv.variant_id IN (
    10351, 62192, 62186, 62187, 62190, 62191, 
    62188, 62189, 19936, 62197, 62198, 
    62222, 62224, 62226, 62227, 62225, 
    62223, 62228, 62231, 62241, 62236, 
    62232, 62238, 62230, 62233, 62229, 
    62239, 62234, 62235, 62240
  )

Query time 0.00075

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "23.29"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "variant_feature_idx",
            "idx_var_feat_pos"
          ],
          "key": "idx_var_feat_pos",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 30,
          "rows_produced_per_join": 30,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "3.76",
            "eval_cost": "3.00",
            "prefix_cost": "6.76",
            "data_read_per_join": "34K"
          },
          "used_columns": [
            "variant_id",
            "position"
          ],
          "attached_condition": "(`cscart_db`.`pfv`.`variant_id` in (10351,62192,62186,62187,62190,62191,62188,62189,19936,62197,62198,62222,62224,62226,62227,62225,62223,62228,62231,62241,62236,62232,62238,62230,62233,62229,62239,62234,62235,62240))"
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "cscart_db.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 30,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "13.53",
            "eval_cost": "3.00",
            "prefix_cost": "23.29",
            "data_read_per_join": "224K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}