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 (
    15842, 15840, 15785, 15841, 16154, 16846, 
    16060, 16066, 16061, 16062, 16063, 
    16064, 16065, 15769, 15496, 15497, 
    15768, 15770
  )

Query time 0.00057

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "25.21"
    },
    "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": 18,
          "rows_produced_per_join": 18,
          "filtered": "100.00",
          "index_condition": "(`dev_yourmart_co_bw`.`p`.`product_id` in (15842,15840,15785,15841,16154,16846,16060,16066,16061,16062,16063,16064,16065,15769,15496,15497,15768,15770))",
          "cost_info": {
            "read_cost": "10.81",
            "eval_cost": "1.80",
            "prefix_cost": "12.61",
            "data_read_per_join": "288"
          },
          "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": [
            "dev_yourmart_co_bw.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 18,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "4.50",
            "eval_cost": "1.80",
            "prefix_cost": "18.91",
            "data_read_per_join": "7K"
          },
          "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": [
            "dev_yourmart_co_bw.p.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 18,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "4.50",
            "eval_cost": "1.80",
            "prefix_cost": "25.21",
            "data_read_per_join": "1K"
          },
          "used_columns": [
            "feature_id",
            "purpose",
            "group_id"
          ]
        }
      }
    ]
  }
}