Cloud SQL: ACE Exam Study Guide (2026)

Cloud SQL

Image source: Google Cloud Documentation

1. Core Overview

Cloud SQL is a fully managed relational database service (RDBMS) on Google Cloud.

Supported Database Engines: MySQL, PostgreSQL, and SQL Server.
Editions (2026 Standards):
- Cloud SQL Enterprise: Standard performance and reliability.
- Cloud SQL Enterprise Plus: Enhanced performance, higher availability (99.99% for regional), and near-zero downtime maintenance.
Use Cases: Web frameworks, structured data, existing applications that require standard SQL, OLTP workloads.

Cloud SQL Index Advisor automatically analyzes query patterns and recommends new indexes to improve performance. It identifies slow or inefficient queries, suggests optimal indexes, and can show the expected impact before applying changes. It helps reduce manual tuning and keeps databases performing efficiently.

2. High Availability (HA) and Replication

Understanding the difference between HA and Read Replicas is heavily tested on the ACE exam.

High Availability (HA)

Purpose: Protection against zone failures. Provides reliability, not performance scaling.
Architecture: Regional configuration. Provisions a Primary instance in one zone and a Standby instance in another zone within the same region.
Failover: Automatic. If the primary zone goes down, the standby takes over.

Read Replicas

Purpose: Read performance scaling (offloading read queries from the primary instance).
Architecture: Can be in the same region or a different region (Cross-Region Read Replica).
Failover: Manual. You must manually promote a read replica to become a standalone primary instance if needed for disaster recovery.

3. Backups and Recovery

Automated Backups: Taken daily within a configurable backup window. Retained for up to 365 days.
On-Demand Backups: Taken manually at any time.
Point-in-Time Recovery (PITR): Allows you to restore an instance to a specific fraction of a second.
Cloning: You can clone a Cloud SQL instance to create an exact, independent copy.

4. Scaling

Vertical Scaling: Increasing the machine type (vCPUs and RAM). Requires a restart of the database instance.
Horizontal Scaling: Using Read Replicas to scale read capacity. Cloud SQL does not natively horizontally scale for write operations (use Cloud Spanner or AlloyDB for massive write scale).
Storage Auto-Increase: Cloud SQL can automatically add storage capacity as you approach your limit.
Important Fact: Cloud SQL storage can scale up (requires downtime), but it cannot scale down.

5. Security and Networking

Private IP: Instances can have a private, internal IP via Private Services Access (VPC Peering).
Cloud SQL Auth Proxy: The Gold Standard for secure connections. It uses IAM for authentication and automatically handles SSL/TLS. No need to whitelist IP addresses when using the proxy.
IAM Authentication: Allows users and service accounts to log in using their Google Cloud identity instead of static database passwords.

6. Maintenance

Maintenance Windows: You define a specific day and time when Google can perform updates.
Impact: Maintenance usually results in a brief period of downtime (minimized in Enterprise Plus edition).

7. Decision Tree for the ACE Exam

Structured data / Relational? -> Cloud SQL or Spanner.
Local/Regional scale? -> Cloud SQL.
High performance PostgreSQL requirements? -> AlloyDB.
Global scale or massive writes? -> Cloud Spanner.
Petabytes of data / Data Warehousing / OLAP? -> BigQuery.
Unstructured data / NoSQL? -> Cloud Firestore or Cloud Bigtable.

8. Migration and Administrative Tasks

Database Migration Service (DMS): The primary tool for migrations from on-premises or other clouds to Cloud SQL.
Import/Export: You MUST store the SQL/CSV file in a Cloud Storage (GCS) bucket first before importing it into Cloud SQL.
Service Account Permissions: The Cloud SQL Service Account must have roles/storage.objectViewer on the GCS bucket for imports.

9. Using Cloud SQL in a Spring Boot App (Example)

Connect to Cloud SQL (PostgreSQL) using its IP, just like a regular PostgreSQL instance.

spring:
  datasource:
    url: jdbc:postgresql://10.0.0.10/DB_NAME?currentSchema=SCHEMA_NAME
    username: USER
    password: PASSWORD
    driver-class-name: org.postgresql.Driver

  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true

When to Use Each Cloud SQL Connection Method

Private IP

Use it when your service runs inside a VPC (GKE, GCE, Cloud Run with VPC connector). Best security and lowest latency. No public exposure.
Cloud SQL Auth Proxy

Use for local development or when you want automatic IAM auth and secure TLS without managing certificates. Works anywhere but adds a sidecar/agent.
```
./cloud-sql-proxy INSTANCE_CONNECTION_NAME \
    --port=5432 \
    --credentials-file=key.json
```
For more details see Connect using the Cloud SQL Auth Proxy (Google Cloud Documentation).

Socket Factory (JDBC Connector)

Use in Java apps (Spring Boot) when you want secure IAM‑based connections without running the proxy. Common in Cloud Run and GKE.

spring:
datasource:
  url: jdbc:postgresql://google/DB_NAME?socketFactory=com.google.cloud.sql.postgres.SocketFactory&cloudSqlInstance=INSTANCE_CONNECTION_NAME
  username: USER
  password: PASSWORD
  driver-class-name: org.postgresql.Driver

10. Exam Tip

Private IP → Best for production inside a VPC (GKE, GCE, Cloud Run + VPC connector)
Auth Proxy → Easiest secure option for local dev or simple setups
Socket Factory → Ideal for Java apps needing secure IAM auth without running the proxy

GCP ACE - Study Guide (2026)