Model Provider Selection: Routing, Fallbacks, and Commercial vs Open Models

Model provider selection interviews examine how you avoid single-vendor fragility while controlling quality and cost. Interviewers ask about routing policies, fallback chains, and how you eval when a provider silently updates model weights behind a version label.

Commercial APIs offer capability and compliance features—VPC endpoints, zero-retention agreements, fine-tuning—but at variable pricing. Candidates compare token pricing, batch discounts, rate limits, and effective cost when long contexts dominate workloads.

Open-weight models on self-hosted infrastructure trade license review and GPU ops for control. Discuss when Llama-class models suffice for extraction and routing, when you still need frontier models for reasoning, and how you benchmark on your data—not public leaderboards alone.

Data residency and regulatory constraints often dictate provider choice. Articulate regional deployment patterns, logging policies, and how you prevent customer data from crossing borders through tool calls or support tickets sent to vendor dashboards.

Operational concerns include key rotation, per-tenant API keys, budget caps, and anomaly detection on token spikes. Interviewers want routing that degrades gracefully—cheaper model, shorter context, async batch—before hard failures reach users.