The maintenance window is a time window during which the nodes behind Aiven services are switched to new upgraded version and, once the process is completed, the overall URI DNS name is pointed at the new location.
The upgrade is done during the maintenance window that you can set from the Aiven Console, in service details page. During the maintenance window some services could have a minimal downtime period.
For example, if there is a mandatory service updates for Apache Kafka®, the following upgrade procedure is executed.
Aiven service upgrades are performed in rolling forward style, which means that new service nodes are first created alongside with the older nodes one at a time, after which the old nodes are retired.
In case of MySQL®, PostgreSQL® and Redis®* the maintenance window usually lasts around several seconds. The downtime comes from old master stopping itself in a controlled manner and new master executing promotion sequence after this. Once the promotion is complete the old master node starts forwarding requests to the new master node so the service is accessible before DNS updates are propagated, though clients that end up reconnecting to the old master node will see additional disconnection once the old master is permanently retired.
In case of Apache Kafka® and OpenSearch® the service DNS address resolves to all the available service nodes. During an upgrade the DNS address changes to reflect the added and removed nodes. For example, during an Apache Kafka upgrade procedure, a three node plan will have a minimum of three nodes available at all times during the whole upgrade operation.
While the DNS name remains the same, the IP address it points to, will change during a maintenance break. To know more about static IP addresses, check the related documentation.