SELECT 
  cscart_product_prices.product_id, 
  MIN(
    IF(
      cscart_product_prices.percentage_discount = 0, 
      cscart_product_prices.price, 
      cscart_product_prices.price - (
        cscart_product_prices.price * cscart_product_prices.percentage_discount
      )/ 100
    )
  ) AS price 
FROM 
  cscart_product_prices 
WHERE 
  cscart_product_prices.product_id IN (
    32313, 32324, 32404, 32327, 32307, 37416, 
    40914, 37313, 32315, 1415, 32314, 3513, 
    49304, 49324, 49300, 49330, 49337, 
    49302, 49281, 49354, 50056, 50222, 
    49840, 49823, 49944, 49831, 49940, 
    50054, 49841, 50053, 49827, 49939
  ) 
  AND cscart_product_prices.lower_limit = 1 
  AND cscart_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  cscart_product_prices.product_id

Query time 0.00210

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_prices",
          "access_type": "range",
          "possible_keys": [
            "usergroup",
            "product_id",
            "lower_limit",
            "usergroup_id"
          ],
          "key": "product_id",
          "key_length": "3",
          "used_key_parts": ["product_id"],
          "rows": 33,
          "filtered": 99.9960556,
          "index_condition": "cscart_product_prices.product_id in (32313,32324,32404,32327,32307,37416,40914,37313,32315,1415,32314,3513,49304,49324,49300,49330,49337,49302,49281,49354,50056,50222,49840,49823,49944,49831,49940,50054,49841,50053,49827,49939)",
          "attached_condition": "cscart_product_prices.lower_limit = 1 and cscart_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}