Distributed key-value stores (KVSs) have become an important component for data management in cloud applications. Since resources can be provisioned on demand in the cloud, there is a need for efficient node bootstrapping and decommissioning, i.e. to incorporate or eliminate the provisioned resources as a members of the KVS. It requires the data be handed over and the load be shifted across the nodes quickly. However, the data partitioning schemes in the current-state shared nothing KVSs are not efficient in quick bootstrapping. In this paper, we have designed a middleware layer that provides a decentralised scheme of auto-sharding with a two-phase bootstrapping. We experimentally demonstrate that our scheme reduces bootstrap time and improves load-balancing thereby increasing scalability of the KVS.