Comparison chart - Azure Database for PostgreSQL Single Server and Flexible Server
APPLIES TO: 
Azure Database for PostgreSQL - Flexible Server
Overview
Azure Database for PostgreSQL Flexible Server is the next generation managed PostgreSQL service in Azure. It provides maximum flexibility over your database, built-in cost-optimizations, and offers several improvements over Single Server.
Note
For all your new PostgreSQL deployments, we recommend using Flexible Server. However, you should consider your own requirements against the comparison table below.
Comparison table
The following table provides a list of high-level features and capabilities comparisons between Single Server and Flexible Server.
| Feature / Capability | Single Server | Flexible Server |
|---|---|---|
| General | ||
| General availability | GA since 2018 | GA since 2021 |
| PostgreSQL | Community | Community |
| Supported versions | 10, 11 | 11, 12, 13, 14 |
| Underlying O/S | Windows | Linux |
| AZ selection for application colocation | No | Yes |
| Built-in connection pooler | No | Yes (PgBouncer) |
| Uptime SLA | 99.99% SLA | Up to 99.99% SLA |
| Connectivity | ||
| Username in connection string | <user_name>@server_name. For example, pgadmusr@mypgServer |
Just username. For example, pgadmusr |
| lc_collate | English_United States.1252 | en_US.utf8 |
| lc_ctype | English_United States.1252 | en_US.utf8 |
| lc_messages | English_United States.1252 | en_US.utf8 |
| lc_monetary | English_United States.1252 | en_US.utf-8 |
| lc_numeric | English_United States.1252 | en_US.utf-8 |
| lc_time | English_United States.1252 | en_US.utf8 |
| Connection port | 5432 | 5432 (DB), 6432 (PgBouncer) |
| Max. connections | 1982 | 5000 |
| Connections limit configurable? | No | Yes (max_connections parameter) |
| Compute & Storage | ||
| Compute tiers | Basic, General Purpose, Memory Optimized | Burstable, General Purpose, Memory Optimized |
| Burstable SKUs | No | Yes |
| Ability to scale across compute tiers | Can't scale Basic tier | Yes. Can scale across tiers |
| Stop/Start | No | Yes (for all compute SKUs). Only compute is stopped/started |
| Max. Storage size | 1 TB (Basic), 4 TB or 16 TB (GP, MO). Note: Not all regions support 16 TB. | 16 TB |
| Min storage size | 5 GB (Basic), 100 GB (GP, MO) | 32 GB |
| Storage auto-grow | Yes (1-GB increments) | No |
| Max IOPS | Basic - Variable. GP/MO: up to 18 K | Up to 18 K |
| Networking/Security | ||
| Supported networking | Virtual network, private link, public access | Private access (VNET injection in a delegated subnet), public access) |
| Public access control | Firewall | Firewall |
| Private link support | Yes | No |
| Private VNET injection support | No | Yes |
| Private DNS Zone support | No | Yes |
| Ability to move between private and public access | No | No |
| TLS support | TLS 1.2 | TLS 1.2, 1.3 enforced |
| Can turn off SSL | Yes | Yes (set require_secure_transport to OFF) |
| SCRAM authentication | No | Yes |
| High Availability | ||
| Zone-redundant HA | No | Yes (a synchronous standby is established in another zone within a region) |
| Same-zone HA | No | Yes (a synchronous standby is established in the same zone as the primary) |
| HA Configuration | Built-in with storage pinned to a zone. Compute can float across regions. | Physically separate compute & storage provisioned |
| Cost | 1x | 2x (compute + storage) |
| Availability with non-HA configuration | Automatic restart, compute relocation | Automatic restart, compute relocation |
| Protect from zone failure | Compute - Yes. Storage - No | Compute & storage - Yes |
| Protect from region failure | No | No |
| Mode of HA replication | N/A | Postgres physical streaming replication in SYNC mode |
| Standby can be used for read purposes | N/A | No |
| Application performance impact | No (not replicating) | Yes (Due to sync replication. Depends on the workload) |
| Automatic failover | Yes (spins another server) | Yes |
| Application connection string post failover | No change | No change |
| Logical Replication | ||
| Support for logical decoding | Yes | Yes |
| Support for native logical replication | No | Yes |
| Support for PgLogical extension | No | Yes |
| Support logical replication with HA | N/A | Limited |
| Disaster Recovery | ||
| Cross region DR | Using read replicas, geo-redundant backup | Geo-redundant backup (in selected regions) |
| DR using replica | Using async physical replication | Preview |
| Automatic failover | No | No |
| Can use the same r/w endpoint | No | No |
| Backup and Recovery | ||
| Automated backups | Yes | Yes |
| Backup retention | 7-35 days | 7-35 days |
| PITR capability to any time within the retention period | Yes | Yes |
| Ability to restore on a different zone | N/A | Yes |
| Ability to restore to a different VNET | No | Yes |
| Ability to restore to a different region | Yes (Geo-redundant) | Yes (in selected regions) |
| Ability to restore a deleted server | Limited via API | Limited via support ticket |
| Read Replica | ||
| Support for read replicas | Yes | Yes (Preview) |
| Number of read replicas | 5 | 5 |
| Mode of replication | Async | Async |
| Cross-region support | Yes | Yes |
| Maintenance Window | ||
| System scheduled window | Yes | Yes |
| Customer scheduled window | No | Yes (can choose any 1 hr on any day) |
| Notice period | Three days | Five days |
| Maintenance period | Anytime within 15-hrs window | 1 hr window |
| Metrics | ||
| Errors | Failed connections | Failed connections |
| Latency | Max lag across replicas, Replica lag | N/A |
| Saturation | Backup storage used, CPU %, IO %, Memory %, Server log storage limit, server log storage %, server log storage used, Storage limit, Storage %, Storage used | Backup storage used, CPU credits consumed, CPU credits remaining, CPU %, Disk queue depth, IOPS, Memory %, Read IOPS, Read throughput bytes/s, storage free, storage %, storage used, Transaction log storage used, Write IOPS, Write throughput bytes/s |
| Traffic | Active connections, Network In, Network out | Active connections, Max. used transaction ID, Network In, Network Out, succeeded connections |
| Extensions | (offers latest versions) | |
| TimescaleDB, orafce | Yes | Yes |
| PgCron, lo, pglogical | No | Yes |
| pgAudit | Preview | Yes |
| Security | ||
| Azure Active Directory Support(AAD) | Yes | Yes |
| Customer managed encryption key(BYOK) | Yes | Yes |
| SCRAM Authentication (SHA-256) | No | Yes |
| Secure Sockets Layer support (SSL) | Yes | Yes |
| Other features | ||
| Alerts | Yes | Yes |
| Microsoft Defender for Cloud | Yes | No |
| Resource health | Yes | Yes |
| Service health | Yes | Yes |
| Performance insights (iPerf) | Yes | Yes. Not available in portal |
| Major version upgrades support | No | Preview |
| Minor version upgrades | Yes. Automatic during maintenance window | Yes. Automatic during maintenance window |
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