Wordpress Website Down

The errors you're encountering indicate that your WordPress website is unable to write to the database because it's currently in read-only mode. This is a common issue that can occur in AWS RDS (Relational Database Service) environments, especially if you're using a multi-AZ setup or have recently performed a failover.

Here are some potential reasons and solutions:

1. Database Failover: If you're using a multi-AZ RDS setup, a failover might have occurred, causing the standby instance to become the primary. Sometimes, the new primary can temporarily remain in read-only mode.

2. Maintenance or Updates: AWS might be performing maintenance on your RDS instance, temporarily putting it in read-only mode.

3. Storage Issues: If the database has reached its storage limit, it might switch to read-only mode to prevent data corruption.

To resolve this:

1. Check your RDS console to see if there are any ongoing operations or recent events that might explain the read-only state.

2. If using multi-AZ, try forcing a failover back to the original primary instance.

3. Restart your RDS instance if no critical operations are in progress. This often resolves temporary read-only states.

4. Verify that your database has sufficient storage space and increase it if necessary.

5. Check if any recent configuration changes might have affected the database's write permissions.

6. If the issue persists, contact AWS support for further assistance.

Remember to be cautious when making changes to your database setup, especially if you're new to AWS. It's always a good idea to have recent backups before attempting any significant changes.
Sources
Lightsail/Wordpress site mysteriously down and inaccessible | AWS re:Post
Wordpress Running on EC2 goes down | AWS re:Post
Achieve faster switchover for Amazon RDS Blue/Green Deployments with large number of connections | AWS Database Blog

Hello.

Where is the database running?
If you are using RDS Aurora, the reader endpoint may be referenced on the WordPress side, so please check whether you are using the correct endpoint on the WordPress side.
Also, if you are using RDS, make sure the "read_only" parameter is set to False in the parameter group.
https://repost.aws/knowledge-center/rds-read-replica