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

Senior
May 2026

Summary

OpenAI system design round for a software engineering role. The question was about designing Sora, which sounds cool on the surface but quickly turns into a pretty deep conversation about failure handling once you get past the high-level architecture.

Questions Asked (1)

Q1

Design Sora (OpenAI's video generation system), including a high-level system overview followed by a deep dive into the scheduler component and its failure cases.

System DesignTechnical Trade-offsRoot Cause Analysis
Author's notes

The high-level part felt manageable but the scheduler deep dive is where things got real.

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AI HintsAI Generated

Suggested Approach

Start by outlining the end-to-end pipeline for video generation, from user prompt to final video, highlighting key components like the diffusion model, text encoder, and scheduler. Then, zoom into the scheduler, explaining its role in orchestrating the denoising steps, and discuss failure modes such as timeouts, resource contention, and model errors, along with mitigation strategies.

Pro tip: Emphasize trade-offs between latency, quality, and cost, and how the scheduler balances these. Show awareness of OpenAI's scale and reliability requirements by discussing monitoring and graceful degradation.

1. High-Level System Overview

Describe the overall architecture: user interface, API gateway, prompt processing, model inference (diffusion), video encoding, and storage. Mention scalability and distributed components.

2. Scheduler Role and Responsibilities

Explain that the scheduler manages the denoising steps, allocates compute resources, handles batching, and ensures timely completion. It coordinates between the diffusion model and other services.

3. Scheduler Design Details

Discuss the scheduler's internal design: job queue, priority handling, resource allocation (GPU/TPU), step sequencing, and integration with model serving. Mention techniques like dynamic batching and preemption.

4. Failure Cases and Mitigation

Identify potential failures: node crashes, network partitions, model errors, timeouts, resource exhaustion. For each, propose mitigation: retries, fallbacks, circuit breakers, monitoring, and alerting.

5. Trade-offs and Scalability

Discuss trade-offs: latency vs. quality (number of denoising steps), cost vs. performance, and how the scheduler adapts to varying load. Mention autoscaling and load shedding.

Key Points to Mention

  • Diffusion model inference and denoising steps
  • Scheduler's role in batching and resource allocation
  • Fault tolerance: retries, idempotency, and checkpointing
  • Monitoring and observability for scheduler health
  • Trade-offs between latency, quality, and cost
  • Scalability considerations for high-volume video generation

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