▁during ▁P , ▁and ▁L / C ▁during ▁E . ▁Cos mos ▁DB ▁never ▁viol ates ▁the ▁specified ▁consist ency ▁level , ▁so ▁it ’ s ▁formally ▁CP . ▁ ▁MongoDB ▁can ▁be ▁class ified ▁as ▁a ▁PC / EC ▁system . ▁In ▁the ▁bas eline ▁case , ▁the ▁system ▁guarante es ▁reads ▁and ▁writes ▁to ▁be ▁consistent . ▁ ▁P N UT S ▁is ▁a ▁PC / EL ▁system . ▁ ▁Haz el cast ▁I MD G ▁and ▁indeed ▁most ▁in - memory ▁data ▁gr ids ▁are ▁an ▁implementation ▁of ▁a ▁PA / EC ▁system ; ▁Haz el cast ▁can ▁be ▁configured ▁to ▁be ▁EL ▁rather ▁than ▁EC . ▁Fa una DB ▁implements ▁Cal vin , ▁a ▁transaction ▁protocol ▁created ▁by ▁Dr . ▁Daniel ▁Ab adi ▁and ▁author ▁of ▁P AC EL C ▁theorem , ▁and ▁offers ▁users ▁adjust able ▁controls ▁for ▁L C ▁trade off . ▁It ▁is ▁PC / EC ▁for ▁strictly ▁serial izable ▁transactions , ▁and ▁EL ▁for ▁serial izable ▁reads . ▁ ▁See ▁also ▁▁ ▁C AP ▁theorem ▁ ▁Cons ist ency ▁model ▁ ▁F alla cies ▁of ▁Dist ributed ▁Comput ing ▁ ▁P ax os ▁( comput er ▁science ) ▁ ▁Project ▁management ▁triangle ▁ ▁R aft ▁( comput er ▁science ) ▁ ▁Tri lemma ▁ ▁Notes ▁ ▁References ▁ ▁External ▁links ▁▁▁ ▁" Cons ist ency ▁Trade offs ▁in ▁Modern ▁Dist ributed ▁Database ▁System ▁Design ", ▁by ▁Daniel ▁J . ▁Ab adi , ▁Y ale ▁University ▁Original ▁paper ▁that ▁formal ized ▁P AC EL C ▁