Question 316344 in Azure Question posted in
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what is the Azure Appservice SLA with High availability configured

I do know that the SLA of Appservice plan is 99.95 but when i configure high availability i assume the SLA’s to be higher but i dont see any documentation which says about the SLA can any one help

I tried to search online couldn’t find anything

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Answers


  1. 0

    Yes, A 99.95% uptime.

    Azure App Service is an HTTP-based service for hosting web applications, REST APIs, and mobile back ends. Microsoft guarantees that Azure App Service will be available 99.95% of the time when running on either a single instance or on multiple instances However, no SLA is provided using either the Free or Shared tiers.

    For documentation about your SLA you can contact your Microsoft Support Team.
    Also, you can read more:

    Azure App Service and reliability – Microsoft Azure Well-Architected.

    High Availability in Azure: App Service, Function Apps.

    How SLA 99.95% logically achieved when deploying apps

    Hope this is helpful.

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  2. 0

    The SLAs for Azure and other Microsoft Online Services are frequently updated, you can access them through this resource: Service Level Agreements (SLA) for Online Services

    As of Jan 2024, App Service SLA is 99.95%, so compensation is not triggered until Downtime is more than 0.05% of the Maximum Available Minutes.

    Your assumption is incorrect.
    High Availability configurations for App Services DOES NOT offer better compensation levels and there is not a different SLA. High Availability is instead considered a Shared Responsibility, you can achieve better than 99.95% uptime for your Application by deploying it to a HA configuration might still expereience 6-7 minutes of downtime during scale-out events, which you might be tempted to argue would violate 99.99% if they tried to offer it to you. To actually make your application responsive during such events requires not just infrastructure configuration but also for your application to support failover of the processing to the redundant resources that have been made highly available through pre-emptive provisioning.

    Implementing High Availability focuses more on managing the reliability and preparing for failure, it is not about MS guaranteeing a higher level of service. This is because App Service, and likely your application is dependent on many other services to even achieve the 99.95% that they do offer. You can for instance configure a highly available database cluster with an SLA of 99.99%, Entra ID offers 99.99% as does Azure Cache for Redis and API Management. But App Services internally and the networking stack that gives you secure access to App Services depends on these resources and will always have an individually lower SLA because it is based on aggregating the availability of these other services.

    • Redis does offer a premium 99.999% SLA
    • Cosmos DB offers 99.995% – 99.999% SLA for premium SKUs

    Read more about Reliability in Azure App Service for guidance on best practise for maximising availability of your services, but there is no greater SLA offered for App Service from Microsoft.

    You might consider an MS Partner who might offer you a managed solution with a better SLA but when we start talking about less than 5 minutes downtime a month (~99.99%) for your infrastructure, that doesn’t mean that your application on a single service will not experience greater downtime than that. There are a lot of application logic and other transient infrastructure issues that can occur that mean you will need to architect your application in specific ways to maximise the potential of High Availability.

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