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 (
    6962, 6966, 6967, 6965, 6963, 6952, 6953, 
    6947, 6959, 3425, 6958, 6960, 6968, 
    6961, 6964, 6957, 6956, 6954, 6955, 
    6948, 6950, 6949, 6946, 6945, 3414, 
    6938, 6941, 6944, 3412, 6937, 6939, 
    6943, 6970, 6971, 6972, 6973, 6974, 
    6975
  )

Query time 0.00059

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "79.81"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "p",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "idx_group_id"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "product_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 38,
          "rows_produced_per_join": 38,
          "filtered": "100.00",
          "index_condition": "(`gaseus`.`p`.`product_id` in (6962,6966,6967,6965,6963,6952,6953,6947,6959,3425,6958,6960,6968,6961,6964,6957,6956,6954,6955,6948,6950,6949,6946,6945,3414,6938,6941,6944,3412,6937,6939,6943,6970,6971,6972,6973,6974,6975))",
          "cost_info": {
            "read_cost": "22.81",
            "eval_cost": "3.80",
            "prefix_cost": "26.61",
            "data_read_per_join": "608"
          },
          "used_columns": [
            "product_id",
            "parent_product_id",
            "group_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "g",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "id"
          ],
          "key_length": "3",
          "ref": [
            "gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 38,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "9.50",
            "eval_cost": "3.80",
            "prefix_cost": "39.91",
            "data_read_per_join": "14K"
          },
          "used_columns": [
            "id",
            "code"
          ]
        }
      },
      {
        "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": [
            "gaseus.p.group_id"
          ],
          "rows_examined_per_scan": 3,
          "rows_produced_per_join": 114,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "28.50",
            "eval_cost": "11.40",
            "prefix_cost": "79.81",
            "data_read_per_join": "11K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}