Cloud SQL vs AlloyDB: Choose the Right Managed Postgres (2026)

Google Cloud offers two families of managed RDB services: Cloud SQL and AlloyDB for PostgreSQL. Cloud SQL is the standard managed offering for MySQL / PostgreSQL / SQL Server, while AlloyDB is a high-performance PostgreSQL-compatible DB positioned as an Aurora alternative. This article compares them in detail.

Key Comparison Table

Item	Cloud SQL	AlloyDB for PostgreSQL
Supported engines	MySQL / PostgreSQL / SQL Server	PostgreSQL-compatible only
Performance	Standard (on par with OSS)	4x PG, 100x analytics (official)
HA SLA	99.95% (Regional Instance)	99.99% (Regional)
Pricing	Standard (mid)	~1.5-2x (high)
Max instance size	96 vCPU / 624 GB	128 vCPU / 864 GB
HTAP	—	Built-in Columnar Engine
Vector search	pgvector (PG only)	AlloyDB AI (ScaNN-optimized)
Cross-region replica	Yes	Yes
Main use cases	Standard OLTP, legacy compatibility	High-perf OLTP + analytics + ML

Cloud SQL Details

Pricing and Specs

vCPU x $0.04+/hr + memory + storage
Editions: Enterprise / Enterprise Plus (high-speed storage, CMEK)
Up to 96 vCPU, 624 GB memory, 64 TB storage
SLA: Regional Instance 99.95%, Zonal 99.5%

Main Features

Automatic backups + Point-in-time Recovery
Read Replica (same region / cross-region)
Cloud SQL Auth Proxy (IAM auth + TLS)
Database Migration Service integration
Maintenance Window for planned downtime
CMEK / VPC SC / Private IP

AlloyDB for PostgreSQL Details

Differentiating Features

Columnar Engine: Row + columnar store hybrid; 100x faster analytics queries
Adaptive Vacuum: Resolves PostgreSQL autovacuum issues
Index Advisor: ML-based index recommendations
AlloyDB AI: pgvector + ScaNN, Vertex AI Remote Model
Cluster topology: Primary + up to 20 Read Pools (per-node scaling)
SLA 99.99% (Regional cluster)

Operating Modes

AlloyDB: Standard managed offering
AlloyDB Omni: Runs as a container on-prem or in other clouds (Hybrid)

Selection Flow

MySQL / SQL Server required → Cloud SQL
Standard PostgreSQL compatibility + cost focus → Cloud SQL for PostgreSQL
HTAP / mixed analytics / Aurora alternative → AlloyDB
RAG / vector search at the core → AlloyDB AI
Global distribution + strong consistency → Spanner

Comparison Across Clouds

Item	Cloud SQL	AlloyDB	AWS RDS	AWS Aurora	Azure DB for PostgreSQL
PostgreSQL	○	◎	○	◎	○
MySQL	○	—	○	◎	Separate service
SQL Server	○	—	○	—	Separate service
HTAP	—	◎	—	—	—
Vector	pgvector	AlloyDB AI	pgvector	pgvector	pgvector

Database Migration Service (DMS)

Oracle → AlloyDB / Cloud SQL for PostgreSQL (Heterogeneous)
MySQL → Cloud SQL for MySQL (Homogeneous)
PostgreSQL → Cloud SQL / AlloyDB
SQL Server → Cloud SQL for SQL Server
Free (Homogeneous) + minimal-downtime migration

Should I choose Cloud SQL or AlloyDB?

Standard PostgreSQL compatibility + cost focus → Cloud SQL. High performance + HTAP + Aurora alternative → AlloyDB. If you need MySQL or SQL Server, Cloud SQL is the only choice.

Is AlloyDB fully compatible with PostgreSQL?

Wire protocol compatible with extension support (pgvector, PostGIS, etc.). Some PostgreSQL extensions are reimplemented as managed AlloyDB equivalents.

How big is the price difference?

AlloyDB is roughly 1.5-2x Cloud SQL per compute unit. However, the columnar engine's analytics acceleration and adaptive vacuum optimization can balance out the real total cost.

What are AlloyDB's advantages as an Aurora alternative?

4x faster than PostgreSQL (official benchmark), 100x faster analytics queries (columnar engine), ML integration (Vertex AI Remote Model, pgvector), and a cornerstone of GCP's multi-cloud strategy.

How do HA and DR differ?

Cloud SQL: Regional Instance (HA, 99.95% SLA) + Read Replica. AlloyDB: Primary + Read Pool (HA, 99.99% SLA) + Cross-region Replica.

Does the exam cover Cloud SQL for SQL Server?

Yes, it appears on the PCDBE exam. Cloud SQL fully supports Microsoft-specific features like Windows Authentication, Active Directory integration, SQL Server Audit, and SSRS.

Which is better for vector search (pgvector)?

Both support it, but AlloyDB AI offers higher real-world performance thanks to ScaNN-based optimized search plus hybrid (filter + vector) queries. AlloyDB AI is recommended for RAG use cases.

What about on-premises migration?

Database Migration Service (DMS) enables minimal-downtime migrations: Oracle → AlloyDB / PostgreSQL, MySQL → Cloud SQL, SQL Server → Cloud SQL.

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Author

NicheeLab Editorial Team

NicheeLab editorial team focused on data engineering and cloud certification learning. Content is structured around practical study needs and official exam domains.

Cloud SQL vs AlloyDB: Complete Comparison and How to Choose a Managed PostgreSQL DB on GCP