# general
v //By concurrently safe, we mean that it is thread safe, as well as multi-process safe. This means that if an operation is not idempotent (like signing up a new user based on their email), doing that operation in parallel across different cores should have the same effect that these operations were instead run in a sequence. This in turn implies that we will have to use mutex locking with a core, or db transactions (with row level locking), or some concensus algorithm, or some distributed locking system. //