SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    11236, 11235, 11234, 11233, 11232, 11231, 
    11230, 11229, 11228, 11227, 11226, 
    11225, 11224, 11223, 11222, 11221, 
    11220, 11219, 11218, 11217, 11216, 
    11215
  ) 
  AND feature_id IN (553, 624, 623) 
  AND lang_code = 'en'

Query time 0.00306

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.04"
    },
    "table": {
      "table_name": "cscart_product_features_values",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "fl",
        "lang_code",
        "product_id",
        "fpl",
        "idx_product_feature_variant_id"
      ],
      "key": "idx_product_feature_variant_id",
      "used_key_parts": [
        "product_id",
        "feature_id",
        "lang_code"
      ],
      "key_length": "12",
      "rows_examined_per_scan": 69,
      "rows_produced_per_join": 69,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "9.14",
        "eval_cost": "6.90",
        "prefix_cost": "16.04",
        "data_read_per_join": "53K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`gaseus`.`cscart_product_features_values`.`product_id` in (11236,11235,11234,11233,11232,11231,11230,11229,11228,11227,11226,11225,11224,11223,11222,11221,11220,11219,11218,11217,11216,11215)) and (`gaseus`.`cscart_product_features_values`.`feature_id` in (553,624,623)) and (`gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id feature_id variant_id
11215 553 1324
11215 623 1975
11215 624 1705
11216 553 1324
11216 623 2082
11216 624 1705
11217 553 1324
11217 623 2092
11217 624 1705
11218 553 1324
11218 623 2083
11218 624 1705
11219 553 1324
11219 623 2084
11219 624 1705
11220 553 1324
11220 623 2085
11220 624 1705
11221 553 1324
11221 623 2086
11221 624 1705
11222 553 1324
11222 623 2087
11222 624 1705
11223 553 1324
11223 623 2088
11223 624 1705
11224 553 1324
11224 623 2089
11224 624 1705
11225 553 1324
11225 623 2093
11225 624 1705
11226 553 2197
11226 623 1975
11226 624 1705
11227 553 2197
11227 623 2082
11227 624 1705
11228 553 2197
11228 623 2092
11228 624 1705
11229 553 2197
11229 623 2083
11229 624 1705
11230 553 2197
11230 623 2084
11230 624 1705
11231 553 2197
11231 623 2085
11231 624 1705
11232 553 2197
11232 623 2086
11232 624 1705
11233 553 2197
11233 623 2087
11233 624 1705
11234 553 2197
11234 623 2088
11234 624 1705
11235 553 2197
11235 623 2089
11235 624 1705
11236 553 2197
11236 623 2093
11236 624 1705