PostgreSQL & MySQL
Flexible Server · HA · Read replicas · Version support
Practice questions for this topic →
Flexible Server facts
| Feature | PostgreSQL Flexible Server | MySQL Flexible Server |
|---|---|---|
| Zone-redundant HA | Synchronous standby (zone-redundant by default in most regions); a WAL replica server in a separate zone keeps commit quorum | See the MySQL high availability article on Learn |
| Read replicas | Up to 5, asynchronous; cross-region replicas can be promoted for DR | Read replicas, including cross-region |
| Backup storage | ZRS with zone-redundant HA; LRS for zonal servers and regions without zones | — |
| Legacy | — | Single Server retired Sep 16, 2024 |
MySQL version support
| Version | Standard support ends | Extended Support |
|---|---|---|
| 5.7 | Sep 30, 2026 | Oct 1, 2026 to Mar 31, 2029 |
| 8.0 | Jan 31, 2027 | Feb 1, 2027 to May 31, 2029 |
| 8.4 | Supported (GA) | — |
| 9.5 | Innovation release in public preview | — |
Servers on unsupported versions are automatically enrolled in Extended Support and automatically charged for it.
Facts to know
- When the PostgreSQL standby is temporarily unavailable, commits succeed on the primary plus the WAL replica, so committed data stays durable; failover promotes only the standby.
- Read replicas are for offloading reads where a short lag is acceptable; they don't suit workloads that need up-to-the-second data and don't reduce write load on the primary.
Exam Tips
Tick each tip once you can answer it without looking.
“Open-source PostgreSQL app, managed, zone failure with zero data loss” → PostgreSQL Flexible Server with zone-redundant HA.
“Offload BI queries from PostgreSQL primary” → Read replica (async, may lag). Trap: Not for workloads needing up-to-the-second data.
“Regional DR for PostgreSQL/MySQL” → Cross-region read replica, promote on disaster (or geo-redundant backup restore).
“MySQL Single Server appears as an option” → Pick Flexible Server: Single Server is retired.
“Avoid extended support charges on MySQL 5.7” → Upgrade to MySQL 8.0/8.4.
“Distributed PostgreSQL for multitenant scale-out” → Elastic clusters (Citus) / Cosmos DB for PostgreSQL.
“PostgreSQL zone-redundant HA while the standby is temporarily down” → A WAL replica server in another zone keeps commit quorum, so commits stay durable. Trap: Failover promotes only the standby, never the WAL replica.
“Backup storage for a PostgreSQL server with zone-redundant HA” → Zone-redundant storage (LRS for zonal servers or regions without zones). Trap: Read replicas are asynchronous, up to five per primary.
“MySQL 8.0 support dates” → Standard support ends Jan 31, 2027; Extended Support Feb 1, 2027 to May 31, 2029. Trap: MySQL 5.7 standard support ended Sep 30, 2026; Extended Support runs to Mar 31, 2029.
“MySQL server on an unsupported version after standard support” → Automatically enrolled in Extended Support and charged for it. Trap: MySQL 9.5 is an Innovation release in preview.