SELECT 
  cscart_product_point_prices.product_id, 
  MIN(
    cscart_product_point_prices.point_price
  ) AS point_price 
FROM 
  cscart_product_point_prices 
WHERE 
  cscart_product_point_prices.product_id IN (12855, 12856, 12551) 
  AND cscart_product_point_prices.lower_limit = 1 
  AND cscart_product_point_prices.usergroup_id IN (0, 0, 1)

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_point_prices",
      "access_type": "ref",
      "possible_keys": ["unique_key", "src_k"],
      "key": "unique_key",
      "key_length": "2",
      "used_key_parts": ["lower_limit"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100,
      "index_condition": "cscart_product_point_prices.product_id in (12855,12856,12551) and cscart_product_point_prices.usergroup_id in (0,0,1)"
    }
  }
}