Technical practice
Optimizing KV Cache for Long-Context Serving
What to coverDiscuss the trade-offs between memory consumption and latency when managing KV cache for long-context LLMs. Explain how you would implement or tune techniques like PagedAttention or prompt caching to maintain high throughput without sacrificing stability.
Continuous Batching Strategies
What to coverExplain the mechanics of continuous batching in runtimes like vLLM or SGLang. Describe how you handle the scheduling of requests with varying sequence lengths to maximize GPU utilization and minimize idle time during the decode phase.
Profiling GPU Bottlenecks
What to coverDescribe your methodology for identifying performance bottlenecks in an inference stack. Specifically, how do you differentiate between HBM bandwidth limitations, compute-bound kernels, and NCCL communication overhead in a distributed inference setup?
Speculative Decoding Implementation
What to coverDiscuss the practical challenges of deploying speculative decoding in a production environment. Address how you balance the speedup gained from a draft model against the additional GPU memory and compute overhead required to run it.
Tensor and Pipeline Parallelism Trade-offs
What to coverWhen onboarding a new large-scale model, how do you decide between tensor parallelism and pipeline parallelism? Explain the impact of these strategies on latency, throughput, and the complexity of the underlying NCCL communication patterns.
Quantization for Production Inference
What to coverCompare different quantization methods (e.g., FP8, INT8, AWQ) in terms of their impact on model accuracy versus inference speed. Suggest a strategy for validating these models before rolling them out to production.
Debugging Distributed Inference Failures
What to coverIf a distributed inference service experiences intermittent latency spikes or NCCL timeouts, what steps do you take to isolate the root cause? Mention specific tools or metrics you would inspect across the network and GPU layers.
Runtime Selection and Customization
What to coverGiven the choice between vLLM, TensorRT-LLM, and SGLang, what criteria do you use to select the optimal runtime for a specific model architecture? Explain how you would approach modifying or extending these runtimes to meet unique platform requirements.
Behavioural practice
Translating Technical Metrics to Business Value
What to coverDescribe a situation where you had to justify a complex infrastructure optimization to non-technical stakeholders. How did you connect low-level performance improvements, such as latency reduction, to customer-visible reliability or cost-efficiency?
Collaborating with SRE for Production Stability
What to coverProvide an example of how you have partnered with SRE teams to improve the availability of a production service. Focus on how you defined runtime playbooks or safe defaults to prevent outages during high-traffic periods.
Managing Model Onboarding Risks
What to coverTell us about a time you led the onboarding of a new model into a production environment. How did you handle the transition, including testing, rollback strategies, and ensuring the model met strict latency targets?
Handling Technical Debt in High-Performance Systems
What to coverDescribe a time you identified a performance bottleneck that required significant refactoring of the existing runtime stack. How did you balance the need for immediate production stability with the long-term goal of improving system architecture?