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A shard is a portion of data stored within a cluster. A cluster is made up of multiple shards, each containing a unique subset of the overall dataset. Together, these shards form the complete data store. Shard management includes tasks like:
  • Replication
  • Backup
  • Failover/switchover configuration
  • Monitoring
These tasks are the responsibility of the user, not SPQR. SPQR was originally designed to enable PostgreSQL sharding on top of managed cloud database services. While it simplifies query routing across shards, it does not aim to be a complete shard management system. There are no current plans to release a fully open-source shard management solution as part of SPQR. Instead, users are encouraged to build PostgreSQL clusters using established high-availability (HA) tools such as:
  • Patroni
  • PgConsul
  • Stolon
  • Managed PostgreSQL offerings
These tools rely on physical quorum-based HA mechanisms, which are proven to be reliable and compatible with SPQR. Importantly, SPQR does not manage or control the individual shards. It only requires:
  • Connection information for each shard
  • The data range assigned to each shard
That’s all SPQR needs to route queries correctly.