# Consistency

Consistency in the context of distributed systems revolve around two things, safety and liveness.

## Eventual consistency

Makes promises about liveness only.

## Strong eventual consistency

Makes promises about liveness and safety

## Liveness

The property that eventually something good will happen. For example saying that a system will return a result to every API call is a liveness property.

## Safety

The property states that nothing bad will ever happen. For example never returning a wrong value or electing two leaders.