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 (
    6902, 7017, 6920, 7110, 7272, 6833, 6841, 
    7147, 7153, 6837, 7000, 6831, 6835, 
    7155, 6891, 6952, 6917, 6836, 6839, 
    7146, 6847, 6834, 6838, 7059, 7118, 
    6931, 7130, 6849, 6900, 6848, 6832, 
    7116, 7078, 6886, 7308, 6872, 7160, 
    6888, 7274, 7129
  ) 
  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 0.00165

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "28.01"
    },
    "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": 40,
        "rows_produced_per_join": 7,
        "filtered": "19.99",
        "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`product_id` in (6902,7017,6920,7110,7272,6833,6841,7147,7153,6837,7000,6831,6835,7155,6891,6952,6917,6836,6839,7146,6847,6834,6838,7059,7118,6931,7130,6849,6900,6848,6832,7116,7078,6886,7308,6872,7160,6888,7274,7129))",
        "cost_info": {
          "read_cost": "27.21",
          "eval_cost": "0.80",
          "prefix_cost": "28.01",
          "data_read_per_join": "191"
        },
        "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)))"
      }
    }
  }
}