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 (
    829, 847, 824, 828, 836, 826, 825, 845, 
    851, 865, 858, 843, 859, 863, 834, 827, 
    830, 846, 835, 864, 844, 861, 849, 862, 
    850, 833
  )

Query time 0.00237

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "104.26"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "gp",
          "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": 85,
          "rows_produced_per_join": 85,
          "filtered": "100.00",
          "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`gp`.`group_id` in (829,847,824,828,836,826,825,845,851,865,858,843,859,863,834,827,830,846,835,864,844,861,849,862,850,833))",
          "cost_info": {
            "read_cost": "36.26",
            "eval_cost": "8.50",
            "prefix_cost": "44.76",
            "data_read_per_join": "1K"
          },
          "used_columns": [
            "product_id",
            "group_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "gpf",
          "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.gp.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 85,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "21.25",
            "eval_cost": "8.50",
            "prefix_cost": "74.51",
            "data_read_per_join": "8K"
          },
          "used_columns": [
            "feature_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": 85,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "21.25",
            "eval_cost": "8.50",
            "prefix_cost": "104.26",
            "data_read_per_join": "65K"
          },
          "used_columns": [
            "feature_id",
            "product_id",
            "variant_id",
            "lang_code"
          ]
        }
      }
    ]
  }
}