Hello @Rajarshi Haldar
Welcome to Microsoft Q&A Platform,
The 3-tier model is perfectly applicable on Azure, please check the articles below:
https://learn.microsoft.com/en-us/azure/architecture/guide/architecture-styles/n-tier
https://learn.microsoft.com/en-us/azure/architecture/reference-architectures/n-tier/n-tier-sql-server
https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/migrate/azure-best-practices/migrate-best-practices-networking#best-practice-design-subnets
I hope this helps!
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