A public web application on App Service must reach a 99.95 percent SLA and keep running if one datacenter inside its region fails, without a manual switch. Which configuration satisfies this?
Show answer and explanation
Answer: C
An App Service Environment with zone redundancy spreads instances across availability zones in the region. That provides the 99.95 percent SLA and keeps the app running if one datacenter fails. Several instances in a single zone protect only against instance failure. Separate plans behind DNS do not fail over automatically, and deployment slots manage releases rather than adding availability.
Why the other options are wrong
- A. Several instances in one zone protect against instance failure, but a datacenter outage in that zone takes the whole app down, so the zonal SLA is not reached.
- B. Two plans with DNS switching need manual or DNS-driven changes and share no health model, so failover is neither automatic nor covered by an availability SLA.
- D. Slots let you stage code and swap traffic during releases. They do not place workloads across zones and do not protect against a datacenter failure.
Exam tip. Zone-level resilience for App Service comes from zone redundancy, not from deployment features.