SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12855, 12854, 12853, 10412, 10411, 10410, 
    10409, 10408, 10407, 10406, 15781, 
    10405, 10404, 10403, 10402, 10401, 
    10400, 10399, 10398, 10397
  )

Query time 0.00047

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 20,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (12855,12854,12853,10412,10411,10410,10409,10408,10407,10406,15781,10405,10404,10403,10402,10401,10400,10399,10398,10397)"
    }
  }
}