Turo·Software Engineer·Onsite - System Design / Architecture·Senior

SeniorPrefer not to say

Jun 2026Remote

Summary

System design round at Turo for a software engineer role. The whole thing was basically one big infrastructure problem about upgrading a production database without blowing up the app.

Questions Asked (1)

You have an app tier talking to a primary DB for writes and a replica for reads. Walk through how you'd upgrade the database from one major version to another with minimal or zero downtime.

System DesignTechnical Trade-offs

Author's notes

This is the kind of question where you can go in a hundred directions and none of them feel fully right.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the constraints: acceptable downtime, data volume, and version compatibility. Then propose a phased approach using logical replication or a blue-green deployment to minimize downtime, with a rollback plan. Emphasize testing and monitoring at each stage.

Pro tip: Mention that you'd first test the upgrade on a staging environment with production-like data and load, and use feature flags to control read/write traffic during cutover. This shows you prioritize safety and user experience.

1. Assess and Plan

Evaluate the current database version, target version, compatibility issues, and required downtime. Define success criteria and rollback strategy.

2. Set Up Replication

Establish logical replication from the old primary to a new primary running the upgraded version. Keep the old replica for reads until cutover.

3. Test and Validate

Run the upgraded database in parallel, replaying production traffic or using a staging environment to validate performance and data integrity.

4. Cutover with Minimal Downtime

Pause writes briefly, ensure replication catches up, promote the new primary, and redirect the app tier to the new primary and replica.

5. Monitor and Rollback if Needed

Closely monitor the new setup for errors or performance issues. If problems arise, roll back to the old primary using the reverse replication path.

Key Points to Mention

Logical replication or change data capture (CDC) for near-zero downtime
Blue-green deployment strategy for database upgrades
Backward compatibility of schema changes and application code
Thorough testing in a staging environment with production-like load
Rollback plan and data consistency checks
Monitoring and alerting during and after cutover

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.