Nexus Gateway
Intelligently routes every prompt to the cheapest foundation model clearing the quality bar, failing over silently during provider degradation.
Engineering highlights
The core architectural breakthroughs.
High-scale engineering demand distilled into four verified production milestones.
Monthly foundation model expenditure dropped from $340,000 to $118,000
Lightweight embedding classifiers evaluate prompt depth in real time
In-flight token streaming spliced to secondary provider during outages
Sub-5ms responses served directly from distributed Redis clusters
Executive overview
The engineering challenge & solution.
The client's AI platform monthly inference spend was surging past $340,000 across OpenAI and Anthropic. Simultaneously, third-party provider outages, sudden 429 rate limit throttles, and degraded latency regularly caused broken user sessions, with no unified monitoring or automated fallback mechanism.
We engineered an intelligent LLM proxy and routing mesh written in TypeScript and Rust. The gateway assesses prompt complexity using a lightweight embedding classifier, routing simple parsing tasks to cost-effective models while reserving expensive frontier models for deep reasoning. A distributed Redis semantic cache intercepts repeated requests.
Engineering governance
The three non-negotiables.
These are the architectural constraints that shaped every boundary — no trade-offs or compromises permitted.
Sub-50ms Silent Failover
When a primary model provider degrades or throws a 5xx error, traffic must reroute to a secondary provider without breaking client streams.
Semantic Prompt Caching
Identical or semantically equivalent prompt inputs must return sub-10ms cached answers without incurring model API costs.
Per-Tenant Budget Enforcement
Enforce strict enterprise token quotas and budget guardrails with real-time financial tracking.
Seamless In-Flight Token Stream Splicing During Provider Mid-Generation Outages
When an upstream provider drops an active SSE connection 40 tokens into an 800-token answer, a standard retry causes the client to receive duplicate text or an unhandled JSON parse error.
We built a bidirectional streaming buffer inside the Envoy gateway. If an active socket disconnects or stalls for more than 400ms, the gateway immediately spins up a secondary provider with the partial generation history prepended as an assistant prefix, splicing the stream seamlessly into the user's active connection.
Request lifecycle
How data moves through Nexus Gateway.
Production verification
Measured outcomes in production.
Every metric below was captured under real production traffic and audited against historical baseline data.
Operational resilience
Automated safety guardrails.
Systems fail in production. Here is how Nexus Gateway survives network partitions, upstream timeouts, and anomalous inputs without human intervention.
Dynamic Provider Circuit Breaker
Automatically shunts traffic away from degraded APIs within 3 failed requests.
Hard Tenant Token Buckets
Redis-backed rate limiters enforce contractual tenant tier limits.
Automated Cost Anomaly Killswitch
Stops runaway agent loops from consuming excess enterprise credits.
Next step
Building a system with this level of demand?
Bring us the constraint that keeps your engineering leadership up at night — the latency ceiling, the compliance perimeter, or the unyielding reliability requirement.