The one thing to understand first
Azure HorizonDB is Microsoft’s cloud-native, PostgreSQL-compatible database, introduced in late 2025 as the step beyond Flexible Server. Where Flexible Server is community Postgres on a disk, HorizonDB belongs to the disaggregated, log-is-the-database family alongside Aurora and AlloyDB: it separates an elastic compute tier from a distributed storage layer so the two scale independently. (HorizonDB is a new, fast-evolving service — always confirm current specifics against Microsoft’s official documentation.)
Disaggregated storage and elastic compute
HorizonDB is built on open-source PostgreSQL but rehosts storage as a distributed, multi-tenant service with tiered caching, so compute nodes do not own their data on a local disk. That separation is what lets the service scale compute up to large core counts, add read capacity, and grow storage independently — the same architectural lever that powers every member of this family. Microsoft positions it for demanding, large-scale transactional workloads that a single Flexible Server primary cannot satisfy.
PostgreSQL compatibility and AI integration
Because it tracks open-source PostgreSQL, HorizonDB aims to keep your SQL, drivers, and much of the extension ecosystem working. Microsoft emphasises tight integration with its AI platform — vector search (pgvector-style) and connectivity to Azure’s AI/agent tooling — reflecting the industry-wide push to make the operational database the home of embeddings and retrieval for AI applications.