API Specification and Policy Updates in Azure APIM Are Zero Downtime

Does APIM support zero downtime deployment? — To answer this question, multiple factors need to be ascertained, like, What is the SKU? Have you opted for Availability zones? etc. In fact, the question needs to be qualified further. What do you mean by zero downtime deployment?

In the case of APIM, there are infrastructure changes and then there are gateway configuration changes like API specifications and policies. So, the answer depends on — SKU, AZ, “what” kind of changes

From the official documentation:

“When you change availability zone configuration, the changes can take 15 to 45 minutes or more to apply. The API Management gateway can continue to handle API requests during this time.”

Gateway configuration, such as APIs and policy definitions, regularly synchronizes between the availability zones that you select for the instance. Propagation of updates between the availability zones normally takes less than 10 seconds.

Active requests: When an availability zone is unavailable, any requests in progress that are connected to an API Management unit in the faulty availability zone are terminated and need to be retried.

Automatic: You can expect instances that use automatic availability zone support to have no downtime during an availability zone outage. Units in the unaffected zone or zones continue to work.

“You can also expect instances that use automatic availability zone support, but have a single unit, to have no downtime.” In this case, API Management distributes the unit’s underlying compute resources to two zones. The resource in the unaffected zone continues to work.

Zone-redundant: You can expect zone-redundant instances to have no downtime during an availability zone outage.

My personal view based on this is —API specifications and Policy updates won’t cause any non-recoverable failures to the consumers; provided retry strategy is in place.

Is it zero downtime? Zero downtime need not mean every request succeeds on the first attempt. If the system remains available and failures are recoverable, it meets the zero-downtime requirement. So — Yes.

Confirmation from Microsoft Question and Answer Forum To validate my understanding, I reached out to the MS Q&A forum and got a response consistent to the above understanding.

Here is the link to the question in the forum that has the official response.

Bottom line — API specification and Policy updates are zero downtime.