If an sd card is too slow and too unreliable for you, considering the full price of a raspberry pi (including case, fan, psu etc) you might be better served by

If an sd card is too slow and too unreliable for you, considering the full price of a raspberry pi (including case, fan, psu etc) you might be better served by some intel based small computer, like a thin client or some small form factor computer (hp, dell, lenovo have many models, that can also be acquired super cheap on ebay and similar).