# Cloud SQL Core Concepts

Cloud SQL provides managed relational databases, abstracting the underlying
infrastructure while offering standard database engines.

## Supported Engines

Cloud SQL supports the following database engines (see [supported
versions](https://docs.cloud.google.com/sql/docs/db-versions)):

-   **MySQL:** Versions 5.6, 5.7, 8.0, and 8.4.

-   **PostgreSQL:** Versions 9.6, 10, 11, 12, 13, 14, 15, 16, 17, and 18
    (default).

-   **SQL Server:** 2017 (Express, Web, Standard, Enterprise), 2019, 2022, and
    2025 (Express, Enterprise, Standard).

## Instance Architecture

Each Cloud SQL instance is powered by a virtual machine (VM) running the
database program.

-   **Primary Instance:** The main read/write connection point.

-   **High Availability (HA):** Provides a standby VM in a different zone with
    automatic failover.

-   **Read Replicas:** Used to scale read traffic and provide local access in
    different regions.

## Storage and Networking

-   **Persistent Disk:** Scalable and durable network storage attached to the
    VM.

-   **Connectivity:** Supports Private IP (using VPC peering for MySQL and
    PostgreSQL only; or using private services access or Private Service Connect
    for all Cloud SQL engines) and Public IP (with authorized networks or Auth
    Proxy).

## Pricing

Cloud SQL pricing is based on:

-   **Instance Type:** vCPUs and RAM.

-   **Storage:** Amount of data stored and IOPS.

-   **Networking:** Network egress and IP address usage.

-   **DNS pricing:** Charge is per zone per month (regardless of whether you use
    your zone). You also pay for queries against your zones.

-   **Licensing:** Applies to SQL Server only. In addition to instance and
    resource pricing, SQL Server also has a licensing component. High
    availability, or regional instances, will only incur the cost for a single
    license for the active resource. As a managed service, Cloud SQL does not
    support BYOL (Bring your own license).

For the latest pricing, visit: [Cloud SQL
Pricing](https://cloud.google.com/sql/pricing).