VPC-Hosted vs Fully Self-Hosted LLM?

Why this distinction matters more than most vendors admit

The phrase 'private LLM' gets used loosely. A vendor might call their product private because your data isn't used for model training, even though it still travels through shared API endpoints. That's not the same as VPC-hosted, and it's definitely not self-hosted.

For SMBs in healthcare, finance, or legal services, the routing of data matters as much as the storage of it. A query containing PHI or PII that hits a shared endpoint, even briefly, creates a compliance exposure that a BAA alone doesn't fix. Understanding exactly where inference happens is the question that determines your actual risk posture.

What each deployment model actually means

VPC-hosted means the LLM, whether that's Llama 3.1, Mistral, or a fine-tuned variant, runs inside a Virtual Private Cloud you control. The compute lives in your AWS account, your Azure subscription, or your GCP project. Traffic stays within your network boundary. You don't share inference capacity with other tenants. The cloud provider manages the underlying hardware, so you're not buying GPUs or hiring someone to rack servers, but the logical environment is yours.

Fully self-hosted means you own the hardware. The model runs on servers in your data center or a co-location facility you contract directly. You control the OS, the networking, the power, and the physical access. This is the highest level of control and the highest level of operational overhead. You need a team that can handle CUDA driver updates, cooling, GPU failure, and 24/7 uptime. Most SMBs don't have that team.

The practical difference in security terms is smaller than most people expect. A properly configured VPC with private subnets, no public egress, encrypted storage, and IAM-scoped access is genuinely air-gapped from the public internet. For HIPAA, SOC 2 Type II, and most financial compliance frameworks, a VPC deployment is sufficient. The compliance gap between VPC-hosted and self-hosted is real but narrow. The operational gap is enormous.

When self-hosted is actually the right answer

Self-hosted becomes necessary when your compliance framework explicitly requires physical control of hardware, not just logical isolation. Some FedRAMP High workloads, certain defense contracts, and a small number of state-level healthcare regulations fall into this category. If your legal team or auditor has specifically flagged hardware custody as a requirement, VPC-hosted won't satisfy it.

It also makes sense if you're already running significant on-prem GPU infrastructure for other workloads, because the marginal cost of adding LLM inference is low. If you're starting from zero, the break-even point where self-hosted is cheaper than VPC-hosted typically requires sustained, high-volume inference that most SMBs don't hit for several years.