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 (
    4705, 2315, 1560, 1707, 1913, 1558, 6255, 
    1598, 1596, 1559, 6250, 1556, 6254, 
    6253, 6252, 1914, 6256, 6258, 6257, 
    6290, 6284, 6285, 6971, 1776, 2077, 
    1754, 1681, 6360, 1600, 3421, 5991, 
    6991, 1784, 7064, 6995
  )

Query time 0.00434

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "36.76"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 35,
          "rows_produced_per_join": 35,
          "filtered": "100.00",
          "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`pfv`.`variant_id` in (4705,2315,1560,1707,1913,1558,6255,1598,1596,1559,6250,1556,6254,6253,6252,1914,6256,6258,6257,6290,6284,6285,6971,1776,2077,1754,1681,6360,1600,3421,5991,6991,1784,7064,6995))",
          "cost_info": {
            "read_cost": "21.01",
            "eval_cost": "3.50",
            "prefix_cost": "24.51",
            "data_read_per_join": "39K"
          },
          "used_columns": [
            "variant_id",
            "position"
          ]
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "softwarepirmam_hewadelivard_cscart_4.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 35,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "8.75",
            "eval_cost": "3.50",
            "prefix_cost": "36.76",
            "data_read_per_join": "105K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}