Abstract: Systems and methods are provided for efficiently maintaining a transaction sequence witness service to ensure that requests to read data provide consistent results across all storage nodes in a distributed system. When a storage node receives a request for a data object, the node may obtain—from transaction sequence witness service—the latest sequence number associated with the object. If the sequence number indicates the object has been modified in the period of time since the currently stored version was stored, the node can obtain the current version from persistent storage.

Abstract: Systems and methods are provided for managing data partitions in a distributed storage system and, in particular, the routing data used by the distributed storage system to route requests to the proper caching layers, persistent storage nodes, etc. Data items may be managed in a multi-tier configuration in which they are grouped into different partitions based on their key prefixes, and partitions are grouped into different cells based on key ranges. When partitions are moved from cell-to-cell, or when cells are split, the routing data is changed accordingly. In order to ensure that the correct routing data is used throughout the distributed storage system, a change to routing data may be accompanied by a special barrier record being written to the transaction log of affected partitions.