Client-side logic and storage are increasingly used in web and mobile
applications to improve response time and availability. Current approaches tend
to be ad-hoc and poorly integrated with the server-side logic. We present a
principled approach to integrate client- and server-side storage. We support
mergeable and strongly consistent transactions that target either client or
server replicas and provide access to causally-consistent snapshots
efficiently. In the presence of infrastructure faults, a client-assisted
failover solution allows client execution to resume immediately and seamlessly
access consistent snapshots without waiting. We implement this approach in
SwiftCloud, the first transactional system to bring geo-replication all the way
to the client machine. Example applications show that our programming model is
useful across a range of application areas. Our experimental evaluation shows
that SwiftCloud provides better fault tolerance and at the same time can
improve both latency and throughput by up to an order of magnitude, compared to
classical geo-replication techniques
