Is Aya rare in Warframe?

Excuse me, could you possibly elaborate on the rarity of Aya within the context of the game Warframe? I'm curious to know if Aya is considered a scarce or hard-to-acquire resource within the game's mechanics and economy. Does it play a significant role in progressing through the game, or is it more of a niche item that's only of interest to a select few players? Your insights would be greatly appreciated.