Many do, and even large DBs can be accomodated by throwing terabytes of RAM at the problem, but etcd is fundamentally targeted at a different problem domain tha

Many do, and even large DBs can be accomodated by throwing terabytes of RAM at the problem, but etcd is fundamentally targeted at a different problem domain than a general-purpose database. Everything in etcd is represented by a single-threaded state machine, which is great for simplicity and correctness, but that comes with performance limitations.