很经典的论文Spanner is Google’s scalable, multi-version, globallydistributed, and synchronously-replicated database. It is
the first system to distribute data at global scale and support externally-consistent distributed transactions. This
paper describes how Spanner is structured, its feature set,
the rationale underlying various design decisions, and a
novel time API that exposes clock uncertainty. This API
and its implementation are critical to supporting external consistency and a variety of powerful features: nonblocking reads in the past, lock-free read-only transactions, and atomic schema changes, across all of Spanner.
