Question 1: What are the phases of data migration?

Answer: 1) Assessment (analyze source, schema, volume), 2) Migrate (full load + incremental sync), 3) Validate (data quality, performance), 4) Cutover (switch traffic).

Question 2: What is the difference between online and offline migration?

Answer: Online: Source running during migration (minimal downtime). Offline: Source downtime required. Use online for production; offline for non-critical.

Question 3: When would you use AzCopy vs DMS?

Answer: AzCopy: File-based migrations (terabytes). DMS: Database migrations with ongoing sync. Data Box: Petabyte-scale offline migrations.

Question 4: How do you handle schema changes during migration?

Answer: DMS schema synchronization, post-migration transformation pipelines, schema validation checks, and flexible target schemas.

Question 5: What is CDC-based migration?

Answer: Initial full load + CDC-based incremental sync. Minimizes downtime by keeping source and target in sync until cutover.

Question 6: How do you validate data after migration?

Answer: Row count comparison, checksum/hash validation, aggregate metrics comparison, and application testing against target.

Question 7: What is the benefit of using Azure Data Box?

Answer: Physical device for offline transfer of large datasets (tens of TB to PB). No network bandwidth required. Secure and compliant.

Question 8: How do you migrate from on-premises SQL Server?

Answer: DMS for online migration with CDC, backup/restore for offline, and Synapse PolyBase for bulk loading.

Question 9: What is the difference between migration and modernization?

Answer: Migration: Move as-is to cloud. Modernize: Re-architect for cloud-native capabilities (serverless, managed services).

Question 10: How do you handle data transformation during migration?

Answer: ETL with ADF, Databricks notebooks, or Synapse Pipelines. Transform during migration or post-migration in target.

Question 11: What is the benefit of lift-and-shift migration?

Answer: Fastest migration path, minimal code changes, and immediate cloud benefits (scalability, availability). Good starting point for cloud adoption.

Question 12: How do you migrate data lake workloads?

Answer: AzCopy for file transfer, ADLS Gen2 as target, Delta Lake for ACID transactions, and Synapse for analytics.

Question 13: What is the benefit of using Databricks for migration?

Answer: Spark-based processing for large-scale transformations, Delta Lake for reliable storage, and notebook development for complex logic.

Question 14: How do you handle data governance during migration?

Answer: Purview for discovery, classification, and lineage. Maintain governance policies throughout migration process.

Question 15: What is the difference between rehosting and refactoring?

Answer: Rehost: Lift-and-shift (minimal changes). Refactor: Modify for cloud-native capabilities. Rehost is faster; refactoring provides long-term benefits.

Question 16: How do you migrate streaming workloads?

Answer: Event Hubs for ingestion, Stream Analytics for processing, and parallel running during transition period.

Question 17: What is the benefit of phased migration?

Answer: Reduces risk, enables learning, allows parallel running, and provides rollback capability at each phase.

Question 18: How do you handle data dependencies during migration?

Answer: Map dependencies, migrate in dependency order, maintain referential integrity, and validate cross-system relationships.

Question 19: What is the benefit of using Terraform for migration?

Answer: Infrastructure as code for reproducible environments, version control, and consistent deployment across environments.

Question 20: How do you optimize migration performance?

Answer: Parallel transfers, appropriate file sizes, compression, network optimization, and staged migration approach.

Question 21: What is the difference between migration and replication?

Answer: Migration: One-time move. Replication: Ongoing synchronization. Use migration for cutover; replication for DR or hybrid scenarios.

Question 22: How do you handle testing during migration?

Answer: Parallel environments, data comparison testing, application testing, performance testing, and user acceptance testing.

Question 23: What is the benefit of using Azure Migrate?

Answer: Discovery, assessment, and migration of on-premises workloads. Provides dependency mapping and right-sizing recommendations.

Question 24: How do you handle rollback during migration?

Answer: Maintain source system, parallel running, checkpoint-based rollback, and automated failover procedures.

Question 25: What is the future of data migration?

Answer: Automated migration tools, continuous migration (not one-time), and cloud-native migration services.