There are many upgrade strategies such as:

• Rolling upgrade

• Blue Green

• A/B testing

• Canary

and they work for apps with shared-nothing-architecture. and some strateigies also work for a distributed clusterd app like rolling upgrade for ElasticSearch

I just need to confirm that either of those strategies doesn't apply to an app that is stateful and doesn't support clustering at data tier. ( such as only one instance of app can write to external Database [ and persistent Volume ] at a time ) ?

So I wonder that the only way to upgrade is to stop and delete the current deployment and deploy a new one , with some down time?