Design a Relational-to-DynamoDB Migration System

Quick Overview

This question evaluates expertise in system design for large-scale relational-to-DynamoDB migrations, including NoSQL data modeling, schema and access-pattern analysis, historical backfill, change-data-capture, validation, cutover and rollback planning, and operational monitoring; it is categorized under System Design and database migration/NoSQL domains. It is commonly asked to assess practical application of architectural concepts and trade-offs required to achieve minimal downtime, ensure data correctness, and maintain availability and observability, emphasizing applied system-level design rather than low-level implementation details.

Design a Relational-to-DynamoDB Migration System

Company: eBay

Role: Software Engineer

Category: System Design

Difficulty: medium

Interview Round: Onsite

Design a production migration system that moves an existing e-commerce service from a relational database to DynamoDB with minimal downtime. Your design should cover: - How to analyze the existing relational schema and access patterns. - How to model the target DynamoDB tables, partition keys, sort keys, and secondary indexes. - How to perform the initial historical backfill. - How to capture and replay ongoing writes while the migration is in progress. - How to validate data correctness between the old and new stores. - How to cut traffic over safely from the relational database to DynamoDB. - How to roll back if the migration causes correctness, latency, or availability problems. - What key indicators you would monitor during the migration and after cutover.

Overview: This question evaluates expertise in system design for large-scale relational-to-DynamoDB migrations, including NoSQL data modeling, schema and access-pattern analysis, historical backfill, change-data-capture, validation, cutover and rollback planning, and operational monitoring; it is categorized under System Design and database migration/NoSQL domains. It is commonly asked to assess practical application of architectural concepts and trade-offs required to achieve minimal downtime, ensure data correctness, and maintain availability and observability, emphasizing applied system-level design rather than low-level implementation details.

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Apr 8, 2026
mediumSoftware EngineerOnsiteSystem Design
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Design a production migration system that moves an existing e-commerce service from a relational database to DynamoDB with minimal downtime.

Your design should cover:

  • How to analyze the existing relational schema and access patterns.
  • How to model the target DynamoDB tables, partition keys, sort keys, and secondary indexes.
  • How to perform the initial historical backfill.
  • How to capture and replay ongoing writes while the migration is in progress.
  • How to validate data correctness between the old and new stores.
  • How to cut traffic over safely from the relational database to DynamoDB.
  • How to roll back if the migration causes correctness, latency, or availability problems.
  • What key indicators you would monitor during the migration and after cutover.

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