PACELC theorem

The Pacelc Theorem is an idea about computers and how they work. It says that when a computer is given two tasks to do, it can either do them quickly (at the same time) or slowly (one at a time). The idea is that if a computer wants to do two things quickly, it has to sacrifice one for the other, which means it won't be able to do both tasks as well as it could if it took a bit longer and did them one at a time.