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 (
    3855, 3859, 5105, 8812, 6163, 6853, 6161, 
    7807, 6061, 6062, 6854, 6060, 7823, 
    7838, 7827, 6821, 7829, 7811, 7866, 
    10103, 6852, 7841, 6850, 6855, 7861, 
    7856, 10160, 7863, 7840, 7812, 7855, 
    7860, 7868, 7869, 7870, 10242, 7813, 
    7825, 8242, 8373
  ) 
  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 0.00220

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "29.36"
    },
    "grouping_operation": {
      "using_filesort": false,
      "table": {
        "table_name": "cscart_product_prices",
        "access_type": "range",
        "possible_keys": [
          "usergroup",
          "product_id",
          "lower_limit",
          "usergroup_id"
        ],
        "key": "product_id",
        "used_key_parts": [
          "product_id"
        ],
        "key_length": "3",
        "rows_examined_per_scan": 43,
        "rows_produced_per_join": 8,
        "filtered": "19.99",
        "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`product_id` in (3855,3859,5105,8812,6163,6853,6161,7807,6061,6062,6854,6060,7823,7838,7827,6821,7829,7811,7866,10103,6852,7841,6850,6855,7861,7856,10160,7863,7840,7812,7855,7860,7868,7869,7870,10242,7813,7825,8242,8373))",
        "cost_info": {
          "read_cost": "28.50",
          "eval_cost": "0.86",
          "prefix_cost": "29.36",
          "data_read_per_join": "206"
        },
        "used_columns": [
          "product_id",
          "price",
          "percentage_discount",
          "lower_limit",
          "usergroup_id"
        ],
        "attached_condition": "((`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`lower_limit` = 1) and (`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`usergroup_id` in (0,1)))"
      }
    }
  }
}