Roblox Senior Software Engineer Interview Questions

Behavioral Questions (15)

1. 1.Tell me about a time you had to optimize performance in a system that needed to serve thousands of concurrent users in real-time. What was your approach and how did you measure success?

   easy~3 min

   What interviewers look for

   • Demonstrates understanding of real-time performance constraints and how they differ from batch processing or traditional web applications
   • Shows experience with profiling, monitoring, and measurement-driven optimization rather than premature optimization
   • Describes collaboration across disciplines (backend, frontend, infrastructure) to solve performance holistically

   Likely follow-ups

   • What specific metrics did you track to validate your optimizations worked?
   • How did you ensure your performance improvements didn't break existing functionality?

   Company context

   Roblox operates one of the largest real-time 3D platforms with millions of concurrent users across experiences. The Real-Time 3D Engineering principle requires engineers to think about graphics, physics, networking, and frame budgets together, making performance optimization a core competency for any senior engineer.

2. 2.You're working on Roblox Studio's asset upload pipeline and notice that large mesh uploads are causing the editor to freeze for 30+ seconds. How would you redesign this to keep the UI responsive?

   easy~4 min

   What interviewers look for

   • Proposes asynchronous processing with progress indicators and background threads
   • Considers chunked uploads or streaming to handle large files gracefully
   • Mentions validation and error handling for malformed assets before blocking operations
   • Discusses caching strategies to avoid re-uploading identical assets

   Likely follow-ups

   • How would you handle the case where a developer tries to upload a 500MB mesh file?
   • What would you do if the upload fails halfway through and the developer wants to retry?

   Company context

   Roblox Studio is used by millions of creators who need fast iteration cycles to build experiences. The Get Stuff Done value means engineers must balance ambitious scope with smooth developer workflows, and Self-Organizing teams own the entire creator experience end-to-end.

3. 3.We want to build a feature that lets Roblox developers A/B test their experiences on live players. Design a system that can handle experiments across 10 million concurrent users while ensuring statistical validity.

   easy~2 min

   What interviewers look for

   • Designs experiment assignment that maintains consistency across user sessions and respects statistical requirements
   • Considers the developer ecosystem perspective, including easy-to-use APIs and clear analytics dashboards
   • Addresses data collection and analysis pipeline that can handle high-volume real-time events
   • Accounts for experiment isolation to prevent conflicts between multiple running tests

   Likely follow-ups

   • How would you handle a developer who wants to test a monetization change that could affect Robux revenue?
   • What safeguards would you put in place if an experiment is causing players to leave an experience?

   Company context

   Roblox's developer ecosystem earned over $1 billion through the platform, making developer success critical to the company's business model. This tests understanding of Roblox's commitment to empowering creators with sophisticated tools while maintaining platform stability and user experience quality.

4. 4.Tell me about a time you had to drive a technical decision across multiple teams without having formal authority over them. What was your strategy for getting buy-in?

   easy~3 min

5. 5.Roblox Studio crashes started spiking 20% yesterday, but we haven't shipped any Studio updates in a week. Walk me through how you'd investigate this and prioritize your hypotheses.

   easy~4 min

6. 6.Describe a feature you built where user safety was a primary consideration. How did you balance user experience with safety requirements?

   medium~4 min

7. 7.Our game servers are seeing memory leaks in long-running Roblox experiences that have been active for 8+ hours. The leak seems related to Lua script garbage collection not cleaning up properly. How would you debug and fix this?

   medium~5 min

8. 8.Design a real-time voice chat system that needs to work across PC, mobile, and VR for up to 50 players in a single Roblox experience. How do you handle the different device capabilities and network constraints?

   medium~3 min

9. 9.Describe a situation where you had to choose between shipping something quickly to meet a deadline versus taking more time to build it properly for the long term. How did you approach that tradeoff?

   medium~4 min

10. 10.Estimate how many concurrent physics calculations Roblox processes globally during peak hours. Walk me through your reasoning and key assumptions.

    medium~5 min

11. 11.Walk me through the most complex API design decision you've made in the last two years. What were the competing requirements and how did you ensure long-term maintainability?

    hard~5 min

12. 12.Design a system to handle Robux transactions for in-experience purchases where we need to process 50,000 transactions per second globally while ensuring no double-spending, even during network partitions.

    hard~5 min

13. 13.Design a system to automatically detect and respond to exploits in user-generated Roblox experiences, where malicious scripts could affect physics, teleport players, or steal virtual items. The system needs to work across 40 million published experiences.

    hard~5 min

14. 14.Walk me through a time when you identified a systemic problem that was affecting multiple teams or products, but wasn't anyone's explicit responsibility to fix. How did you drive a solution?

    hard~5 min

15. 15.Robux spending in experiences dropped 8% month-over-month, but daily active users and session time stayed flat. No major policy or monetization changes shipped. How would you analyze this and what would you investigate first?

    hard~5 min