03-sharded-read-write

Sharding with read/write splitting

This example maps 128 virtual shards over two physical replica sets. Generated routed methods derive the shard key through tenantResolver; reads use replicas by default and writes always use the selected primary.

Required variables are SHARD0_PRIMARY_DSN, SHARD0_REPLICA_DSN, SHARD1_PRIMARY_DSN, and SHARD1_REPLICA_DSN.