SELECT 
  f.feature_id, 
  f.purpose, 
  p.product_id, 
  p.parent_product_id, 
  g.id, 
  g.code 
FROM 
  cscart_product_variation_group_features AS f 
  INNER JOIN cscart_product_variation_groups AS g ON f.group_id = g.id 
  INNER JOIN cscart_product_variation_group_products AS p ON f.group_id = p.group_id 
WHERE 
  p.product_id IN (
    976, 978, 968, 971, 636, 969, 972, 977, 
    1022, 1023, 1106, 1013, 1105, 1101, 
    1104, 979, 989, 632, 613, 617, 621, 622, 
    1015, 1016, 1018, 1019, 611, 612, 980, 
    1007, 1002, 638, 997, 990, 992, 985, 
    1012, 1020
  )

Query time 0.00060

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "191.06"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "p",
          "access_type": "ALL",
          "possible_keys": [
            "PRIMARY",
            "idx_group_id"
          ],
          "rows_examined_per_scan": 353,
          "rows_produced_per_join": 48,
          "filtered": "13.88",
          "cost_info": {
            "read_cost": "63.66",
            "eval_cost": "9.80",
            "prefix_cost": "73.46",
            "data_read_per_join": "783"
          },
          "used_columns": [
            "product_id",
            "parent_product_id",
            "group_id"
          ],
          "attached_condition": "(`cscart`.`p`.`product_id` in (976,978,968,971,636,969,972,977,1022,1023,1106,1013,1105,1101,1104,979,989,632,613,617,621,622,1015,1016,1018,1019,611,612,980,1007,1002,638,997,990,992,985,1012,1020))"
        }
      },
      {
        "table": {
          "table_name": "f",
          "access_type": "ref",
          "possible_keys": [
            "idx_group_id"
          ],
          "key": "idx_group_id",
          "used_key_parts": [
            "group_id"
          ],
          "key_length": "3",
          "ref": [
            "cscart.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 48,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "49.00",
            "eval_cost": "9.80",
            "prefix_cost": "132.26",
            "data_read_per_join": "4K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "g",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "id"
          ],
          "key_length": "3",
          "ref": [
            "cscart.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 48,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "49.00",
            "eval_cost": "9.80",
            "prefix_cost": "191.06",
            "data_read_per_join": "19K"
          },
          "used_columns": [
            "id",
            "code"
          ]
        }
      }
    ]
  }
}