SELECT 
  pfv.feature_id, 
  pfv.product_id, 
  pfv.variant_id, 
  gp.group_id 
FROM 
  cscart_product_features_values AS pfv 
  INNER JOIN cscart_product_variation_group_products AS gp ON pfv.product_id = gp.product_id 
  INNER JOIN cscart_product_variation_group_features AS gpf ON gpf.group_id = gp.group_id 
  AND gpf.feature_id = pfv.feature_id 
WHERE 
  pfv.lang_code = 'en' 
  AND gp.group_id IN (
    330, 320, 317, 322, 324, 323, 318, 315, 
    334, 316, 319, 338, 321, 336, 333
  )

Query time 0.00121

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "44.56"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "gpf",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "idx_group_id"
          ],
          "key": "idx_group_id",
          "used_key_parts": [
            "group_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 16,
          "rows_produced_per_join": 16,
          "filtered": "100.00",
          "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`gpf`.`group_id` in (330,320,317,322,324,323,318,315,334,316,319,338,321,336,333))",
          "cost_info": {
            "read_cost": "9.36",
            "eval_cost": "1.60",
            "prefix_cost": "10.96",
            "data_read_per_join": "1K"
          },
          "used_columns": [
            "feature_id",
            "group_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "gp",
          "access_type": "ref",
          "possible_keys": [
            "PRIMARY",
            "idx_group_id"
          ],
          "key": "idx_group_id",
          "used_key_parts": [
            "group_id"
          ],
          "key_length": "3",
          "ref": [
            "softwarepirmam_hewadelivard_cscart_4.gpf.group_id"
          ],
          "rows_examined_per_scan": 3,
          "rows_produced_per_join": 48,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "12.00",
            "eval_cost": "4.80",
            "prefix_cost": "27.76",
            "data_read_per_join": "768"
          },
          "used_columns": [
            "product_id",
            "group_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "pfv",
          "access_type": "ref",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "lang_code",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "fpl",
          "used_key_parts": [
            "feature_id",
            "product_id",
            "lang_code"
          ],
          "key_length": "12",
          "ref": [
            "softwarepirmam_hewadelivard_cscart_4.gpf.feature_id",
            "softwarepirmam_hewadelivard_cscart_4.gp.product_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 48,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "12.00",
            "eval_cost": "4.80",
            "prefix_cost": "44.56",
            "data_read_per_join": "37K"
          },
          "used_columns": [
            "feature_id",
            "product_id",
            "variant_id",
            "lang_code"
          ]
        }
      }
    ]
  }
}

Result

feature_id product_id variant_id group_id
656 3011 1609 315
656 3012 1559 315
656 3013 1560 315
656 3014 1607 316
656 3015 1559 316
656 3016 1609 317
656 3017 1560 317
656 3018 2758 317
656 3019 3421 317
656 3021 1560 318
656 3022 1559 318
656 3023 1560 319
656 3024 3421 319
656 3026 1596 320
656 3030 1560 320
656 3029 1559 320
656 3031 2077 321
656 3036 1600 321
656 3034 2077 322
656 3033 3442 322
656 3037 1560 323
656 3038 2758 323
643 3039 1591 324
643 3040 1526 324
643 3041 1526 324
656 3039 2077 324
656 3040 1600 324
656 3041 2077 324
656 3055 2315 330
656 3058 1560 330
656 3059 2077 330
656 3066 1560 333
656 3067 2758 333
656 3069 1609 334
656 3070 1559 334
656 3071 1560 334
656 3072 2077 334
656 3602 1560 336
656 3078 1674 336
656 3079 1559 336
656 3080 1600 336
656 3084 1555 338
656 3085 1560 338