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

Senior
Jun 2026

Summary

System design round at OpenAI for a software engineer role. The prompt sounds flashy but it's really just a job scheduler problem, and the interviewer went deep on failure recovery and compute efficiency.

Questions Asked (3)

Q1

Design a large-scale video generation system (essentially a distributed job scheduler with GPU resource management).

System DesignTechnical Trade-offs
Author's notes

The name threw me for a second but once I reframed it as a job scheduler the structure clicked.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scale, then design a high-level architecture that separates job scheduling, GPU resource management, and video generation pipeline stages. Dive into trade-offs for scheduling policies, fault tolerance, and scalability, and discuss how to handle long-running GPU jobs and data movement.

Pro tip: Emphasize the unique challenges of video generation: long-running GPU tasks, large intermediate data, and the need for checkpointing and preemption. Show awareness of cost and utilization metrics to demonstrate production maturity.

1. Clarify Requirements and Scale

Ask about expected job volume, video length/resolution, latency requirements, and GPU types. Define functional and non-functional requirements like throughput, fault tolerance, and cost efficiency.

2. High-Level Architecture

Outline components: API gateway, job queue, scheduler, GPU resource manager, worker nodes, storage for models and outputs, and monitoring. Explain how they interact.

3. Deep Dive into Scheduling and Resource Management

Discuss scheduling algorithms (e.g., bin packing, priority queues), GPU allocation strategies (exclusive vs. shared), and handling of heterogeneous GPUs. Cover preemption, checkpointing, and job priorities.

4. Scalability, Fault Tolerance, and Data Management

Explain how to scale horizontally, handle failures (retries, replication), and manage large video data (distributed storage, caching). Discuss monitoring and autoscaling.

5. Trade-offs and Optimizations

Compare design choices: centralized vs. decentralized scheduling, batch vs. real-time, cost vs. latency. Suggest optimizations like model caching, pipeline parallelism, and spot instance usage.

Key Points to Mention

  • Job scheduling algorithms and queue management (e.g., FIFO, priority, fair share)
  • GPU resource allocation and sharing (MIG, time-slicing, exclusive)
  • Fault tolerance: checkpointing, retries, and idempotency
  • Data management: distributed storage, caching, and data locality
  • Scalability: horizontal scaling, autoscaling, and load balancing
  • Monitoring and metrics: GPU utilization, job latency, cost per video

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

Q2

How would you handle worker failures mid-job: resume from a checkpoint or restart the entire job from scratch?

System DesignTechnical Trade-offs
Author's notes

This is where I felt the most pressure.

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AI HintsAI Generated

Suggested Approach

Start by acknowledging that the decision depends on job characteristics like cost of recomputation, checkpoint overhead, and failure frequency. Then propose a hybrid approach: use checkpoints for long-running jobs with expensive computation, but fall back to restarting for short jobs where checkpointing adds unnecessary complexity. Emphasize that the right choice is a trade-off between recovery time, resource waste, and system complexity.

Pro tip: Mention that checkpointing must be idempotent and consistent—if the checkpoint captures partial state, resuming can produce incorrect results, which is worse than restarting. Also, consider the cost of checkpoint storage and I/O, especially in distributed systems.

1. Clarify job characteristics

Ask about job duration, computation cost, failure frequency, and whether the job is idempotent. This determines whether checkpointing is worth the overhead.

2. Evaluate checkpointing overhead

Consider the cost of writing and reading checkpoints (I/O, storage, serialization) versus the cost of recomputing from scratch. If checkpoint overhead is high relative to job cost, restarting may be simpler.

3. Assess consistency and correctness

Ensure that resuming from a checkpoint yields correct results. Checkpoints must capture a consistent snapshot of state; otherwise, partial failures can lead to data corruption.

4. Choose a strategy based on trade-offs

For long, expensive jobs, use checkpoints to avoid losing progress. For short jobs or when checkpointing is complex, restart from scratch. Consider adaptive strategies like checkpointing only at safe points.

5. Design for failure handling

Implement monitoring, retries, and fallback mechanisms. For example, if checkpoint resume fails, fall back to a full restart. Also, consider distributed coordination if multiple workers are involved.

Key Points to Mention

  • Trade-off between recovery time and checkpoint overhead
  • Idempotency and consistency of checkpoints
  • Cost of recomputation vs. cost of checkpoint storage and I/O
  • Job duration and failure frequency as deciding factors
  • Distributed systems considerations: coordination, partial failures, and exactly-once semantics
  • Adaptive or hybrid strategies (e.g., checkpoint every N steps, or only for long jobs)

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

Q3

How do you prevent wasted GPU compute when a job fails partway through?

System DesignTechnical Trade-offs
Author's notes

Shorter exchange but it cut to the core of the problem.

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AI HintsAI Generated

Suggested Approach

Start by framing the problem as minimizing wasted compute through early failure detection and efficient resource management. Then walk through a layered strategy: checkpointing, health monitoring, and graceful degradation, emphasizing trade-offs between overhead and savings. Conclude with a concrete example from your experience.

Pro tip: Quantify the impact: mention that even a 1% reduction in wasted GPU hours can save millions at scale, showing you understand cost implications. Also, highlight that prevention is better than cure—invest in robust pre-flight checks and validation.

1. Detect failures early

Implement health checks, timeouts, and validation at each stage to catch issues before they consume significant GPU time. Use lightweight probes and fail fast.

2. Checkpoint and resume

Periodically save model state and intermediate results to durable storage, allowing jobs to resume from the last checkpoint instead of restarting from scratch.

3. Isolate and contain

Run jobs in isolated environments (e.g., containers) with resource limits, so a failure in one job doesn't affect others and resources are released promptly.

4. Monitor and auto-remediate

Use monitoring tools to detect anomalies and automatically kill or restart jobs, and alert engineers for manual intervention when needed.

5. Optimize resource allocation

Dynamically allocate GPUs based on job priority and estimated runtime, and use preemption to reclaim resources from low-priority jobs.

Key Points to Mention

  • Checkpointing strategies (frequency, storage overhead, and recovery time)
  • Health monitoring and anomaly detection (e.g., loss spikes, NaN values)
  • Graceful degradation and fallback mechanisms
  • Resource isolation and containerization (e.g., Kubernetes, Docker)
  • Cost-benefit analysis of prevention vs. recovery
  • Real-world example of reducing wasted compute in a previous project

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