RDS maintenance window

The maintenance window in Amazon RDS is a designated time period during which system changes, such as software patching and version upgrades, can be applied to your database instances. However, it's important to understand that not all maintenance activities necessarily result in downtime or immediate changes.

Regarding your specific situation on 13/4/2025 between 1300-1400 (Malaysia Time):

1. Active running during maintenance window: It's normal for your RDS instance to remain active during the maintenance window. The maintenance window is simply a time frame during which maintenance activities may be initiated, but it doesn't mean the instance will be unavailable for that entire period.

2. No version update: Not all maintenance windows will result in visible changes like version updates. Some maintenance activities might involve behind-the-scenes updates or checks that don't require immediate changes to the database version.

3. Downtime during maintenance: Most maintenance events complete within the 30-minute maintenance window without causing significant downtime. However, larger maintenance events may take longer to complete. In many cases, especially for routine updates, you might observe minimal or no effect on performance.

4. Multi-AZ deployments: If you're using a Multi-AZ deployment, maintenance activities are often performed with minimal impact. Amazon RDS typically applies updates to the standby instance first, then promotes it to primary, and finally updates the old primary instance.

5. Deferred maintenance: Some maintenance actions can be deferred. If no critical updates were pending, it's possible that no significant changes were applied during that particular maintenance window.

It's worth noting that while maintenance windows are scheduled weekly, not every window will necessarily involve active maintenance. Amazon RDS aims to minimize disruption to your database operations while ensuring necessary updates are applied for security and performance reasons.

If you have specific concerns about maintenance activities or need to ensure certain updates are applied, you can check the Amazon RDS console, use the AWS CLI, or consult the RDS API to view pending maintenance actions for your instance.
Sources
Maintaining a DB instance - Amazon Relational Database Service
Maintaining an Amazon Aurora DB cluster - Amazon Aurora
Best practices for maintenance activities in Amazon RDS for Oracle | AWS Database Blog

To clarify, the maintenance window in Amazon RDS defines a preferred period when system changes (such as OS updates, instance restarts, or minor engine upgrades) can be applied. However, just because a maintenance window is scheduled doesn't necessarily mean changes will occur during that window; it only means that AWS is allowed to apply pending updates during that time if needed.

In your case, on 13 April 2025, between 13:00 and 14:00 Malaysia Time, although a maintenance window was defined, no version upgrade occurred, and the instance remained in active status. This suggests that either:

There were no pending updates to apply at that time (e.g., no engine patch, security update, or OS-level change), or The update may have been non-disruptive, requiring no downtime (some patches can be applied in-place without reboot, especially on newer instance types with RDS Multi-AZ or enhanced maintenance options).

To answer your core question: Is there downtime during the maintenance window?

Not always. Downtime only occurs if the pending maintenance requires a reboot or restart of the instance. If the maintenance task can be applied without interruption, then the instance remains active. You can also check the RDS Event Logs or AWS Personal Health Dashboard to confirm if any updates were attempted/applied during that window.

If you want full control, you can manage or defer the application of pending updates by modifying the RDS instance and enabling "Apply during the next maintenance window" or applying immediately, depending on your needs.