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 (
    66161, 66168, 66169, 66170, 66171, 66175, 
    66176, 66177, 66178, 66181, 66182, 
    66183, 66187, 66188, 66189, 66190, 
    66194, 66195, 66196, 66201, 66202, 
    66203, 66208, 66209, 66210, 66215, 
    66216, 66222
  )

Query time 0.00101

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "72.84"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "rows_examined_per_scan": 28,
          "rows_produced_per_join": 28,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "33.64",
            "eval_cost": "5.60",
            "prefix_cost": "39.24",
            "data_read_per_join": "126K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ],
          "attached_condition": "((`webmarco`.`pfvd`.`variant_id` in (66161,66168,66169,66170,66171,66175,66176,66177,66178,66181,66182,66183,66187,66188,66189,66190,66194,66195,66196,66201,66202,66203,66208,66209,66210,66215,66216,66222)) and (`webmarco`.`pfvd`.`lang_code` = 'en'))"
        }
      },
      {
        "table": {
          "table_name": "pfv",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "ref": [
            "webmarco.pfvd.variant_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 28,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "28.00",
            "eval_cost": "5.60",
            "prefix_cost": "72.84",
            "data_read_per_join": "31K"
          },
          "used_columns": [
            "variant_id",
            "position"
          ]
        }
      }
    ]
  }
}