If you want no down time, you need to be using slot which is the default option, but with longer deployment time. For hotfix, you might want to consider direct deploy instead https://world.episerver.com/blogs/anders-wahlqvist/dates/2021/3/introducing-direct-deploy-a-quicker-way-to-deploy-to-dxp/ 

Direct deploy is available for the integration environment only.

Hey there Vahid,

There are 2 ways to do this.

If you want to use Visual Studio, you would have to deploy it to Integration and go through the environments as normal (Integration -> Preproduction -> Production). This isnt necessarily a hotfix, but it will get you to production.

The accepted way for hotfixes is to use the Deployment API and deploy straight to Production, which will go to the slot, and then you can either Complete/Reset the deployment. (To be a bit safer, based on how much time you have, you could also go to PreProduction first)

I have documented the process of the Deployment API in my blog posts here: https://optimizelyvisuals.dev/2020/04/episerver-dxp-deployment-api-powershell/

As for downtime, that wont be an issue unless you're doing database updates through Episerver Nuget package updates. If this is the case, not that itll help you right now, you may want to look into smooth deploy.

Smooth Deploy is currently in Beta, but it will help with exactly what you're talking about here. Updates/Hotfixes without any downtime, even if it has database updates: https://optimizelyvisuals.dev/2021/01/episerver-dxp-deployment-api-smooth/ & https://world.episerver.com/documentation/developer-guides/digital-experience-platform/deploying/deployment-process/smooth-deploy/