Azure Cosmos DB for PostgreSQL
deprecatedby Microsoft · since 2019 · also known as Hyperscale (Citus), Azure Database for PostgreSQL Hyperscale (Citus)
Microsoft's managed Citus service for sharded Postgres, now retiring in favor of Elastic Clusters.
deprecated. Microsoft lists it as on a retirement path and not recommended for new projects; use Elastic Clusters in Azure Database for PostgreSQL instead.
Overview
Azure Cosmos DB for PostgreSQL is Microsoft's managed service for Citus, the extension that shards PostgreSQL tables across a coordinator and worker nodes. It began as Hyperscale (Citus) under Azure Database for PostgreSQL and was rebranded under the Cosmos DB umbrella in 2022, despite having nothing in common with Cosmos DB's NoSQL engine. It suited multi-tenant SaaS and real-time analytics that outgrew one Postgres server. Microsoft has since put the service on a retirement path: it is no longer recommended for new projects, and Postgres users are directed to Elastic Clusters in Azure Database for PostgreSQL, which provide the same Citus sharding inside the mainstream Postgres service.
Strengths & trade-offs
Strengths
- +Fully managed Citus with built-in PgBouncer, HA and backups
- +Start on one node and distribute tables later without changing databases
- +Tracks new PostgreSQL majors quickly because Citus is an extension
Trade-offs
- −On a retirement path; no future for new projects
- −Confusing branding: unrelated to Cosmos DB's NoSQL APIs
- −Cross-shard queries on non-distribution columns can be slow
Great for
- +Existing deployments planning migration to Elastic Clusters
- +Multi-tenant SaaS sharded by tenant (legacy)
- +Real-time analytics dashboards (legacy)
Think twice for
- −Any new project
- −Workloads needing multi-region writes
Capabilities
Native or official first-party support · 16 of 25 tracked
Scale & consistency
- Comfortable data size
- Large · ≤ 1 PB
- Horizontal scaling
- Native
- Multi-region
- Read replicas
- Transactions
- Full ACID
- Consistency
- Strong
- Schema
- Strict
- Architecture
- Distributed, Client server
- Query languages
- SQL, PL/pgSQL
Distributed tables across worker nodes with shard rebalancing; HA standbys and cross-region read replicas.
Deployment
available on · Azure
Ecosystem
Alternatives to Azure Cosmos DB for PostgreSQL
Microsoft's managed community PostgreSQL, with zone-redundant HA, DiskANN vectors and Citus elastic clusters.
azure-cosmos-db-for-postgresql vs azure-database-for-postgresql →Postgres extension that shards tables across nodes for multi-tenant SaaS and real-time analytics.
azure-cosmos-db-for-postgresql vs citus →Microsoft's globally distributed, multi-API NoSQL and vector database with SLA-backed latency.
azure-cosmos-db-for-postgresql vs azure-cosmos-db →Apache-licensed distributed SQL that reuses the PostgreSQL query layer on a Raft-replicated storage engine.
azure-cosmos-db-for-postgresql vs yugabytedb →Postgres-wire distributed SQL built to survive node, zone and region failures with serializable transactions.
azure-cosmos-db-for-postgresql vs cockroachdb →Alibaba's open-source, MySQL-compatible shared-nothing distributed SQL with Paxos and columnar indexes.
azure-cosmos-db-for-postgresql vs polardb-x →Azure Cosmos DB for PostgreSQL FAQ
What is Azure Cosmos DB for PostgreSQL?
Azure Cosmos DB for PostgreSQL is a relational database by Microsoft, first released in 2019. Azure Cosmos DB for PostgreSQL is Microsoft's managed service for Citus, the extension that shards PostgreSQL tables across a coordinator and worker nodes. It began as Hyperscale (Citus) under Azure Database for PostgreSQL and was rebranded under the Cosmos DB umbrella in 2022, despite having nothing in common with Cosmos DB's NoSQL engine. It suited multi-tenant SaaS and real-time analytics that outgrew one Postgres server. Microsoft has since put the service on a retirement path: it is no longer recommended for new projects, and Postgres users are directed to Elastic Clusters in Azure Database for PostgreSQL, which provide the same Citus sharding inside the mainstream Postgres service.
Is Azure Cosmos DB for PostgreSQL open source?
No. Azure Cosmos DB for PostgreSQL is proprietary, closed-source software.
Does Azure Cosmos DB for PostgreSQL support ACID transactions?
Yes. Azure Cosmos DB for PostgreSQL supports full ACID transactions, with strong consistency.
Does Azure Cosmos DB for PostgreSQL scale horizontally?
Azure Cosmos DB for PostgreSQL scales horizontally out of the box, with built-in sharding or partitioning. It is comfortable at large scale (≤ 1 PB). It supports cross-region read replicas.
How can I run Azure Cosmos DB for PostgreSQL?
You can use the vendor's managed cloud. It is available on Azure.
What is Azure Cosmos DB for PostgreSQL best for?
Azure Cosmos DB for PostgreSQL is a strong fit for existing deployments planning migration to Elastic Clusters, multi-tenant SaaS sharded by tenant (legacy) and real-time analytics dashboards (legacy). Think twice for any new project.
What are the best alternatives to Azure Cosmos DB for PostgreSQL?
Common alternatives to Azure Cosmos DB for PostgreSQL include Azure Database for PostgreSQL, Citus, Azure Cosmos DB, YugabyteDB and CockroachDB. The right choice depends on your workload, scale and hosting; WhichDB's smart match ranks them against your requirements.
Is Azure Cosmos DB for PostgreSQL still maintained?
Azure Cosmos DB for PostgreSQL is deprecated. Microsoft lists it as on a retirement path and not recommended for new projects; use Elastic Clusters in Azure Database for PostgreSQL instead.
How popular is Azure Cosmos DB for PostgreSQL?
Azure Cosmos DB for PostgreSQL has little measurable public adoption today, so it ranks near the bottom of the WhichDB Score.