Evaluate a Migration from MySQL to MongoDB
ByteDanceSoftware Engineer · Technical ScreenLast updated
Evaluate whether a MySQL-backed service should migrate to MongoDB using its actual workload and correctness needs. Compare relational and document models, joins and transactions, then outline a dual-run migration, rollback plan, and measurements that would prove an improvement.
A team proposes migrating an existing MySQL-backed service to MongoDB. Explain how you would decide whether the migration is justified, compare the data models and consistency needs, execute the migration safely, and prove any claimed improvement.
Constraints & Assumptions
- The current workload and schema are not yet specified, so begin with evidence to collect.
- The system must remain available during migration.
- A technology change is not itself a performance result.
Clarifying Questions to Ask
- Which queries, joins, transactions, and integrity constraints dominate the workload?
- Is the pain write throughput, read latency, schema evolution, operational scaling, or developer workflow?
- What correctness guarantees and rollback window are required?
Follow-up questions
- How would you model data that is read as one aggregate but updated by several independent workflows?
- How would you detect missing or reordered changes during backfill?
- What evidence would make you cancel the migration?
Solution walkthrough is for members
Get the full walkthrough with reference code and complexity analysis, plus Kitty Coach at 300 messages a day. Hints, the code runner and community answers stay free.