SELECT 
  tmall_product_prices.product_id, 
  COALESCE(
    tmall_master_products_storefront_min_price.price, 
    MIN(
      IF(
        tmall_product_prices.percentage_discount = 0, 
        tmall_product_prices.price, 
        tmall_product_prices.price - (
          tmall_product_prices.price * tmall_product_prices.percentage_discount
        )/ 100
      )
    )
  ) AS price 
FROM 
  tmall_product_prices 
  LEFT JOIN tmall_master_products_storefront_min_price ON tmall_master_products_storefront_min_price.product_id = tmall_product_prices.product_id 
  AND tmall_master_products_storefront_min_price.storefront_id = 1 
WHERE 
  tmall_product_prices.product_id IN (
    94, 96, 136, 90, 95, 89, 82, 84, 85, 88, 
    47, 138, 93, 87, 139, 83, 137, 248
  ) 
  AND tmall_product_prices.lower_limit = 1 
  AND tmall_product_prices.usergroup_id IN (0, 1) 
GROUP BY 
  tmall_product_prices.product_id

Query time 0.00802

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.044687897,
    "nested_loop": [
      {
        "table": {
          "table_name": "tmall_master_products_storefront_min_price",
          "access_type": "system",
          "possible_keys": ["PRIMARY"],
          "rows": 0,
          "filtered": 0,
          "const_row_not_found": true
        }
      },
      {
        "table": {
          "table_name": "tmall_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"],
          "loops": 1,
          "rows": 18,
          "cost": 0.03350794,
          "filtered": 97.28681946,
          "index_condition": "tmall_product_prices.product_id in (94,96,136,90,95,89,82,84,85,88,47,138,93,87,139,83,137,248)",
          "attached_condition": "tmall_product_prices.lower_limit = 1 and tmall_product_prices.usergroup_id in (0,1)"
        }
      }
    ]
  }
}