In theory, blockchains are embarrassingly-functional: take a prior state, apply a block to it, and get a new state. However, in practice, every blockchain implementation is filled with memory mutation, database I/O, and other side effects. Spoiler: They simply have too much state! Fortunately, a functional data structure known as a cryptographic accumulator can compress this state to a manageable size. In this talk, Luke will describe how this accumulator works, its broad impact on the system, and the benefits of a blockchain where practice aligns with theory.