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 (
    6903, 7817, 7805, 7819, 7803, 7824, 7905, 
    8336, 7815, 6941, 7121, 7086, 7714, 
    7176, 6938, 6911, 6994, 7084, 6993, 
    6991, 7027, 6939, 7054, 6940, 7169, 
    7120, 7712, 7138, 7095, 7167, 7141, 
    7695, 7031, 7089, 6992, 6892, 7125, 
    6880, 6996, 7173, 7210, 7711, 7715, 
    7792, 7170, 7174, 7087, 7177, 6989, 
    6995, 6997, 7142, 7171, 7172, 7132, 
    7795, 7709, 7806, 7918, 7119, 7696, 
    7793, 7903, 7929, 7931, 7791, 7814, 
    7818, 7822, 7902, 7925, 7928, 7672, 
    7697, 7713, 7790, 7808, 7820, 7821, 
    7831
  ) 
  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 0.00197

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "56.01"
    },
    "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": 80,
        "rows_produced_per_join": 15,
        "filtered": "19.99",
        "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`cscart_product_prices`.`product_id` in (6903,7817,7805,7819,7803,7824,7905,8336,7815,6941,7121,7086,7714,7176,6938,6911,6994,7084,6993,6991,7027,6939,7054,6940,7169,7120,7712,7138,7095,7167,7141,7695,7031,7089,6992,6892,7125,6880,6996,7173,7210,7711,7715,7792,7170,7174,7087,7177,6989,6995,6997,7142,7171,7172,7132,7795,7709,7806,7918,7119,7696,7793,7903,7929,7931,7791,7814,7818,7822,7902,7925,7928,7672,7697,7713,7790,7808,7820,7821,7831))",
        "cost_info": {
          "read_cost": "54.41",
          "eval_cost": "1.60",
          "prefix_cost": "56.01",
          "data_read_per_join": "383"
        },
        "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)))"
      }
    }
  }
}