How would you plan the migration of an on-premises application to the cloud?
What the interviewer wants to hear
- Discovery and assessment of dependencies, data size and constraints
- Choose a strategy per app: rehost, replatform, refactor, retire, retain, repurchase
- Set up landing zone, networking and security first
- Migrate data with replication and plan the cutover with rollback
- Test, then optimize cost and operations after migration
Model answer
I start with discovery: list servers, dependencies, data volumes, performance needs, compliance rules and current costs, often with a discovery tool. Then for each application I pick one of the 7 Rs, such as rehost (lift and shift), replatform (for example moving the database to RDS), refactor, repurchase as SaaS, retire or retain. Before moving anything, I set up a landing zone with accounts, networking, VPN or Direct Connect to the data center, identity and logging. For data, I use continuous replication such as AWS DMS or native database replication, so the final cutover is short. I run the app in parallel, do performance and failover tests, and plan a cutover window with a clear rollback plan, like switching DNS back. After go-live I monitor closely, rightsize resources, and gradually modernize, because the first move is rarely the most cost efficient design.
Can you answer it under time pressure?
Take a timed medium round and get scored on every answer.
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