Design the scheduling and isolation for a multi-tenant fine-tuning service: hundreds of customers, a few base models, shared GPUs.

The expensive thing is a base model in GPU memory, not the customer's job. Keep bases resident, pack LoRA jobs onto them, isolate tenants at the process and device level, checkpoint adapters in seconds so jobs run on cheap capacity, and attribute cost per tenant. The arithmetic behind each rule.

Updated Sep 2026 · Grounded in real AI infrastructure interview loops and written to a senior-engineer editorial bar, with every number worked and every diagram hand-built.

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The concepts behind this question

Ranked by how closely each one overlaps this question's topic, so the first card is the thing to read if the answer above moved too fast.

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📐 AI Systems Design🔒 Premium

Multi-Tenant Fine-Tuning ServiceA fine-tuning service takes a customer's dataset and a base model and returns a model, and the design problem is that many customers want this at once, cheaply, without seeing each other's data, on GPUs that must not sit idle between jobs. LoRA changes the shape: an adapter is a few hundred megabytes rather than a copy of the base, so many jobs can share a base in memory and many adapters can be served from one replica. This page designs the service end to end: the pipeline, the LoRA arithmetic that sets memory and cost, the isolation, the scheduler that packs jobs, and the serving path.

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🗂️ Scheduling & OrchestrationSign in

MIG, MPS and Time-SlicingA whole H100 is far more than a notebook, a small inference service or a CI job needs, and giving each of them a card leaves most of the fleet idle. Three mechanisms share a GPU, and they differ in what they isolate: MIG partitions the hardware into up to seven slices with their own memory and compute, MPS lets several processes share one GPU's SMs concurrently with no memory isolation, and time-slicing context-switches between processes with no isolation at all. The choice is the isolation the workload needs against the utilization the platform wants.

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🗂️ Scheduling & Orchestration🔒 Premium

Multi-Tenancy, Quotas and Fair ShareA shared GPU pool is cheaper than ten private ones because ten teams' demand is smoother than one team's, and it only works if the sharing is enforced. Quotas say what each team is guaranteed, borrowing lets idle guarantees be used by others, fair share decides who waits when everyone wants more, and preemption reclaims borrowed capacity. This page works the arithmetic that makes pooling worth it, the layers of isolation a tenant needs, and the incentive problems (hoarding, gaming, the research-versus-product tension) that any policy has to survive.

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🚀 Inference & Serving🔒 Premium

Multi-LoRA ServingA LoRA adapter is a few hundred megabytes of low-rank matrices that turn a base model into a fine-tuned variant, and multi-LoRA serving runs hundreds of them on one copy of the base weights by keeping the adapters in memory and applying the right one per request inside the batch. It is how a platform serves a thousand customers' fine-tunes without a thousand deployments. The costs are an extra small matmul per layer, adapter memory and loading, and a scheduler that has to batch across adapters without starving any of them.

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UP NEXT ON YOUR JOURNEY

Next in this trackThe cluster dashboard says 90% allocated and 30% utilized. What is happening, how do you prove it, and what policy fixes it?Next in this trackWe have GPUs in two clouds. Can we run one training job across both, and what would you do instead?Next in this trackDesign a notebook platform for 300 researchers on 64 GPUs. How do you share, reclaim and account for the GPUs?

FEDITOR'S NOTE

Scored on base-resident scheduling with the memory arithmetic, on the isolation table per stage, on cheap preemption from small adapter checkpoints, and on cost attribution that charges for the resident base.

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