  Despite decades of research and practical experience, developers have few
tools for programming reliable distributed applications without resorting to
expensive coordination techniques. Conflict-free replicated datatypes (CRDTs)
are a promising line of work that enable coordination-free replication and
offer certain eventual consistency guarantees in a relatively simple
object-oriented API. Yet CRDT guarantees extend only to data updates;
observations of CRDT state are unconstrained and unsafe. We propose an agenda
that embraces the simplicity of CRDTs, but provides richer, more uniform
guarantees. We extend CRDTs with a query model that reasons about which queries
are safe without coordination by applying monotonicity results from the CALM
Theorem, and lay out a larger agenda for developing CRDT data stores that let
developers safely and efficiently interact with replicated application state.
