--- cuppy_hub: azure cuppy_path: reference/postgresql/replicas-upgrades-and-clusters.md cuppy_section: docs cuppy_doc: ZCB1-GMFR cuppy_doc_uuid: 308ff834-93ed-480c-9caa-49b2e07500bf cuppy_permalink: https://cuppy.io/azure/d/ZCB1-GMFR cuppy_version: 1 cuppy_updated: 2026-10-23T16:16:52.575Z cuppy_canonical: https://cuppy.io/azure/docs/reference/postgresql/replicas-upgrades-and-clusters cuppy_mcp: https://cuppy.io/mcp cuppy_body_sha256: a874e6eed93cffd046f12e7d9830b320e81424294667d4a51614d55a0cf1ff57 # cuppy_body_sha256 is over the document body ALONE, excluding both generated blocks. --- # PostgreSQL flexible server operations ## Read replicas - **Up to five replicas per primary**; cascading (each replica with up to five of its own) reaches **30**. Same region or other regions. - General Purpose and Memory Optimized only (**not Burstable**). Replicas have **no high availability and no backups**. - Lag is usually seconds to minutes, and can reach hours under heavy load or across regions: don't read your own writes from a replica. - **Virtual endpoints** give a stable read-write name and a read-only name that keep pointing at the right servers after promotion (not available for cascading replicas). - **Promote** either *to primary server* (roles swap, the old primary becomes a replica) or *to independent server* (it leaves replication). Promotion syncs **planned** (waits for the replica to catch up) or **forced** (immediate, may lose data). - `az postgres flexible-server replica create -g --source-server --name `. ## In-place major version upgrades - The service runs a **precheck**; if it passes, it stops the server, takes an implicit backup, and runs `pg_upgrade`. Versions can be skipped (for example 13 → 16) as long as the target is supported. HA servers lose HA during the upgrade and need capacity to re-create the standby. - **Before you start:** delete read replicas (all of them, cascading too) and re-create them afterwards; keep 10–20% storage free; from 11, switch to **SCRAM** authentication first; avoid long-running transactions. - **Extensions:** drop `session_variable`, `anon` and `age` (they block every upgrade path) and the utility extensions `pg_repack`, `hypopg` and `pg_partman` (drop and re-create); some block only certain targets (`azure_ai`, `azure_storage` and `pg_diskann` for 18, `semver` for 16 and 17, `pg_hint_plan` for 14). Views that depend on `pg_stat_activity` block it too. - Other checks look for logical replication slots, prepared transactions, event triggers and pending restart-required parameters: run the validation before the maintenance window. - **There's no undo**: to go back, restore a point in time before the upgrade onto a new server. - `az postgres flexible-server upgrade -g -n --version 17 --validate-only` runs the checks without upgrading (CLI 2.91 help); drop `--validate-only` to upgrade. ## Elastic clusters (distributed PostgreSQL) **Azure Cosmos DB for PostgreSQL is on a retirement path: new deployments are blocked**; existing clusters stay supported. Its replacement is **elastic clusters** of Azure Database for PostgreSQL flexible server: several flexible-server nodes running Citus, queryable from any node, with managed identity, PgBouncer, up to 3,000 connections per node and the normal compute tiers. Not (yet) available there: VNet integration, TimescaleDB in cluster mode, storage autogrow, long-term retention. Microsoft's snapshot-based migration from Cosmos DB for PostgreSQL usually completes in under 10 minutes with a 5–8 minute read-only window, then you switch connection strings. Versions, extended support and Entra sign-in: `reference/postgresql/flexible-server.md`. --- You are reading one file. The same content is free over MCP at https://cuppy.io/mcp with no signup: ranked search across all 107 documents in this hub, the merged view when you work in a layer, known workarounds matched to the error you hit, and depth control so you spend tokens on what you need. Start with the `_hello` tool. How to connect: https://cuppy.io/azure/ Something wrong in this document? Report it with the `session feedback` tool on the same endpoint.