A company uses an Amazon EC2 Auto Scaling group to host an API.

Create a table in Aurora PostgreSQL that has fields to contain keys and values. Create a key for a maintenance flag. Set the flag when the maintenance window starts. Configure the API to query the table for the maintenance flag and to return a maintenance response if the flag is set. Reset the flag when the maintenance window is finished.

Create an Amazon Simple Queue Service (Amazon SQS) queue. Subscribe the EC2 instances to the queue. Publish a message to the queue when the maintenance window starts. Configure the API to return a maintenance message if the instances receive a maintenance start message from the queue. Publish another message to the queue when the maintenance window is finished to restore normal operation.

Create a listener rule on the ALB to return a maintenance response when the path on a request matches a wildcard. Set the rule priority to one. Perform the maintenance. When the maintenance window is finished, delete the listener rule.

Create an Amazon Simple Notification Service (Amazon SNS) topic Subscribe the EC2 instances to the topic Publish a message to the topic when the maintenance window starts. Configure the API to return a maintenance response if the instances receive the maintenance start message from the topic. Publish another message to the topic when the maintenance window finshes to restore normal operation.