SELECT 
  pfv.feature_id, 
  pfv.product_id, 
  pfv.variant_id, 
  fv.position, 
  fvd.variant 
FROM 
  cscart_product_features_values AS pfv 
  INNER JOIN cscart_product_feature_variants AS fv ON pfv.feature_id = fv.feature_id 
  AND pfv.variant_id = fv.variant_id 
  INNER JOIN cscart_product_feature_variant_descriptions AS fvd ON pfv.variant_id = fvd.variant_id 
  AND fvd.lang_code = 'en' 
WHERE 
  pfv.feature_id IN (549, 548) 
  AND pfv.product_id IN (
    82071, 82118, 82073, 82038, 149042, 
    82061, 81948, 82101, 82009, 81647, 
    82103, 81737, 81655, 81704, 81826, 
    81863, 81860, 81702, 82072, 81634, 
    81657, 81739, 81625, 82115, 81776, 
    82074, 81611, 81862, 81627, 82114, 
    82069, 81817, 81773, 81636, 81812, 
    81624, 81806, 82052, 81816, 82096, 
    81814, 82116, 82095, 81672
  ) 
  AND pfv.lang_code = 'en'

Query time 0.00811

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "147.31"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "variant_id",
            "lang_code",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "lang_code",
          "used_key_parts": [
            "lang_code",
            "feature_id",
            "product_id"
          ],
          "key_length": "12",
          "rows_examined_per_scan": 88,
          "rows_produced_per_join": 88,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "18.83",
            "eval_cost": "17.60",
            "prefix_cost": "36.43",
            "data_read_per_join": "68K"
          },
          "used_columns": [
            "feature_id",
            "product_id",
            "variant_id",
            "lang_code"
          ],
          "attached_condition": "((`webmarco`.`pfv`.`feature_id` in (549,548)) and (`webmarco`.`pfv`.`product_id` in (82071,82118,82073,82038,149042,82061,81948,82101,82009,81647,82103,81737,81655,81704,81826,81863,81860,81702,82072,81634,81657,81739,81625,82115,81776,82074,81611,81862,81627,82114,82069,81817,81773,81636,81812,81624,81806,82052,81816,82096,81814,82116,82095,81672)) and (`webmarco`.`pfv`.`lang_code` = 'en'))"
        }
      },
      {
        "table": {
          "table_name": "fv",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY",
            "feature_id"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "ref": [
            "webmarco.pfv.variant_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 4,
          "filtered": "5.00",
          "cost_info": {
            "read_cost": "88.00",
            "eval_cost": "0.88",
            "prefix_cost": "142.03",
            "data_read_per_join": "5K"
          },
          "used_columns": [
            "variant_id",
            "feature_id",
            "position"
          ],
          "attached_condition": "(`webmarco`.`fv`.`feature_id` = `webmarco`.`pfv`.`feature_id`)"
        }
      },
      {
        "table": {
          "table_name": "fvd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "webmarco.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 4,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "4.40",
            "eval_cost": "0.88",
            "prefix_cost": "147.31",
            "data_read_per_join": "19K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}