A SaaS analytics company runs a multi-tenant PostgreSQL workload on-premises. The largest tenant table has grown to 12 TB, and both transactional inserts and large analytical aggregation queries have become slow because a single node can no longer handle the volume. The team wants a managed Azure service that horizontally scales storage and compute across multiple nodes by distributing (sharding) tables, while keeping full PostgreSQL compatibility so their existing application queries continue to work. Which storage solution should you recommend?