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 (
    2186, 1651, 1682, 1640, 1670, 1650, 1681, 
    1630, 1660, 1649, 1680, 1648, 1679, 
    1647, 1678, 1632, 1662, 2184
  )

Query time 0.00030

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "2.33"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "f",
          "access_type": "ALL",
          "possible_keys": [
            "idx_group_id"
          ],
          "rows_examined_per_scan": 2,
          "rows_produced_per_join": 2,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.52",
            "eval_cost": "0.20",
            "prefix_cost": "0.72",
            "data_read_per_join": "208"
          },
          "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": [
            "cscartdevel.f.group_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 2,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "0.50",
            "eval_cost": "0.20",
            "prefix_cost": "1.42",
            "data_read_per_join": "800"
          },
          "used_columns": [
            "id",
            "code"
          ]
        }
      },
      {
        "table": {
          "table_name": "p",
          "access_type": "ALL",
          "possible_keys": [
            "PRIMARY",
            "idx_group_id"
          ],
          "rows_examined_per_scan": 2,
          "rows_produced_per_join": 4,
          "filtered": "100.00",
          "using_join_buffer": "hash join",
          "cost_info": {
            "read_cost": "0.51",
            "eval_cost": "0.40",
            "prefix_cost": "2.33",
            "data_read_per_join": "64"
          },
          "used_columns": [
            "product_id",
            "parent_product_id",
            "group_id"
          ],
          "attached_condition": "((`cscartdevel`.`p`.`group_id` = `cscartdevel`.`f`.`group_id`) and (`cscartdevel`.`p`.`product_id` in (2186,1651,1682,1640,1670,1650,1681,1630,1660,1649,1680,1648,1679,1647,1678,1632,1662,2184)))"
        }
      }
    ]
  }
}