ken stager — ai solutions architect · digital realty

I architect enterprise AI systems — and own them end to end.

I'm the sole AI Solutions Architect behind Praxo, Digital Realty's Azure-deployed enterprise AI platform, available to ~4,000 employees. Before AI, I founded and ran a company for five years — I bring a founder's ownership to systems engineering.

receipts, not adjectives — every number on this page traces to a maintained claims registry.

~4,000 eligible employees · ~600 monthly active [deployed]
88% measured routing accuracy across five domains [measured]
3,000+ automated tests across the platform ecosystem [verified]
32% → 0% fallback to the legacy path, after a router fix [measured]

[flagship]

Praxo — one platform, five systems.

Praxo — formerly Digital Nexus — is Digital Realty's enterprise AI platform: general AI chat, citation-backed document intelligence, and brand-templated presentation generation, deployed on Azure behind enterprise authentication. I'm its sole AI Solutions Architect — I own the platform's architecture, present it at architecture review boards, and review code for most of the department. Here are five of its systems, the decisions behind them, and what we measured.

nexus/routing

Domain agent orchestration

python · azure functions · semantic kernel · azure openai · reciprocal rank fusion · asyncio

[problem]

One retrieval strategy couldn't reliably serve the range of enterprise questions. Compliance, product, facility, network, and pricing queries each needed a different approach — without sacrificing latency, resilience to partial failures, or a safe rollout path.

[architecture]

An LLM router classifies intent into one of five domains through an explicit state machine — every routing decision lands in an enumerated, testable outcome rather than free-form agent planning. Domain agents retrieve in parallel, results merge through Reciprocal Rank Fusion, and timeouts preserve partial results instead of zeroing out the response.

Chose deterministic routing over free-form agent planning — traded flexibility for auditability and testability.

One tradeoff was accepted deliberately: a measured +7% in end-to-end latency bought an 18% reduction in response-generation time — improving the part of the wait users actually feel.

[measured]

  • 88% measured routing accuracy [measured]
  • Fallback to the legacy path reduced from 32% to 0% after a router fix [measured]
  • Parallel router classification saves 500–1,500 ms per query [measured]
  • 360 automated tests [verified]

Rolled out behind feature flags and validated in shadow mode — the new path ran alongside the legacy path, with per-prompt deltas, before activation. Now live in production as the platform's retrieval backbone.

nexus/retrieval

Retrieval & knowledge layer

azure cognitive search · graphrag · hybrid search · entity resolution · knowledge graphs · postgresql

[problem]

RAG pipelines tend to retrieve too much, too loosely — wasting context budget and raising hallucination risk. Enterprise content needs exact matches and fuzzy ones, plus relationships that vector similarity alone can't see.

[architecture]

Hybrid retrieval combines vector and keyword search, behind layered query understanding: rewrite, decomposition, entity extraction, and geographic entity resolution. A GraphRAG enrichment layer traverses knowledge-graph relationships with typed seed extraction and relevance scoring, and character-budget management compresses what finally reaches the model.

Retrieval and reasoning are separate layers — each gets its own controls, ranking, and evaluation.

[measured]

  • Graph-guided filtering narrowed 80 candidate sites to 3 relevant matches — a 71% reduction in context size [measured]
  • Geographic resolution maps 68 cities, validated by a 43-case stress bench with 99 assertions [verified]

Responses are citation-backed — provenance is part of the architecture, not a display detail.

nexus/reliability

Reliability harness & backend integration

fastapi · postgresql + pgvector · semantic kernel · pydantic · pytest · feature flags · shadow mode

[problem]

Leadership-driven platform consolidation required integrating a production Python AI backend into a broader monorepo — with consistent LLM client behavior, robust persistence, and no silent regressions along the way.

[architecture]

A FastAPI backend with async persistence on PostgreSQL and pgvector, LLM orchestration unified through Semantic Kernel. Structured outputs enforce schemas at every trust boundary, more than eight feature flags gate each new capability, and shadow-comparison tooling runs the legacy and new paths side by side with per-prompt deltas and aggregate reports.

Testing is architecture — the test suite is the contract that lets the platform change safely.

[measured]

  • 2,260 automated tests passing (12 skipped) in this integration alone [verified]
  • Part of a 3,000+ test surface across the platform ecosystem [verified]

The validation posture here set the department's pattern — I review code for most of the department.

nexus/governance

Migration assessment & governance

verification-first assessment · decision logs · msal authentication · event-driven pipelines · stakeholder alignment

[problem]

The platform needed an evidence-based path for a potential port to a broader internal platform — spanning authentication, storage, retrieval infrastructure, and feature parity — without resting on assumptions.

[architecture]

A five-phase, verification-first assessment: discovery, foundation, core capabilities, feature and UX, operations, synthesis. Every architectural decision — authentication strategy, event-driven text extraction, provider selection — is logged with an audit trail so stakeholders can trace the reasoning, not just the conclusion.

Architecture is a communication job — decisions are logged, presented, and defensible.

[measured]

  • Five logged architecture decisions to date; first two phases complete, third in progress [documented]

I lead the program and present findings to architecture review boards and executive stakeholders.

praxo/api-portal

AI API Developer Portal

governed ai gateway · approval-gated provisioning · key lifecycle · usage metering · cost showback

[problem]

Every team that wants to build with the organization's AI models needs credentials, quotas, and accountability — and ad-hoc key sharing doesn't survive an enterprise. Developers needed self-service access; the platform needed governance that can't be bypassed.

[architecture]

My own creation, designed and built from the ground up as lead: a governed AI gateway that brokers the organization's models behind one managed upstream credential consumers never see. Developers request access through a portal; approval is the sole gate; provisioning flows through a transactional outbox with a reconciler that detects drift and cancels anything that tries to route around the approval path. Keys are generated once, revealed once, rotated on demand — and every subscription is metered, with token usage rolled up into per-team cost showback.

One managed credential upstream, zero shared secrets downstream — access is a governed grant, not a copied key.

[delivered]

  • Live in production — request-to-provision flow verified end to end [deployed]
  • Least-privilege by construction: provisioning roles can create access but can never read keys [confirmed]
  • Per-subscription usage metering and cost showback, priced from a versioned rate book [deployed]

Architecture adversarially reviewed before build — every design draft went through independent cross-model review, and the findings shaped the system.

[engagement]

Microsoft — from MVP to dropping the flag.

From April to July 2026, Microsoft contracted me directly to help carry an internal AI agent from beta to full production — both rollout flags dropped. The product stays confidential; the work is the story.

microsoft/evals

Evaluation platform & production activation

ai agent evaluation · llm-as-judge · regression statistics · release readiness · feature-flag activation

[problem]

An AI agent at MVP is a demo with potential. Shipping it inside Microsoft meant being able to show how it behaved — across the range of things real users would ask — before anyone dropped the flag.

[built]

My largest contribution was the agent's evaluation platform, originated and built end to end: independent quality instruments whose deltas had to agree before a result counted, a harness that exercised the real published agent through the full production path rather than the API, and the statistical discipline — paired tests, false-discovery control, practical-significance thresholds — to tell genuine regressions from noise.

An MVP becomes a product when you can prove how it behaves.

That evidence became the release gate: I authored and published the go/no-go readiness assessment behind the production rollout.

[delivered]

  • The agent shipped: beta flag removed, streaming rolled out to production [delivered]
  • Go/no-go readiness assessment authored and published — verdict: ready [delivered]
  • Evaluation platform originated and built end to end [confirmed]
  • Direct engagement, April–July 2026 [confirmed]

Product identity withheld — internal Microsoft work, described at capability level. The same NDA hygiene applies to every engagement on this page.

[also.built]

[arc]

From owning businesses to owning platforms.

  1. [act-i] 2014–2021

    Builder's foundation

    First employee at a Philadelphia creative agency, where I built its photography division from scratch. Then I founded Penn360, an architectural photography and marketing consultancy I ran for five years — leading a team, managing finance and clients, and operationalizing 3D modeling and drone services. I learned how systems succeed or fail by owning the outcomes.

  2. [act-ii] 2022–2024

    The AI transition

    Enterprise sales at BlueConic taught me how large organizations actually buy and adopt software — and gave me a working fluency in international data law and ethical data handling. I formalized my AI skills at Columbia Engineering's AI/ML program, then applied them immediately in healthcare consulting, where the measure of success was operational relief, not novelty.

  3. [act-iii] 2025–present

    Platform builder

    Sole AI Solutions Architect at Digital Realty. I own the platform end to end — frontend, orchestration, document pipelines, retrieval, cloud deployment — and drove its evolution from Digital Nexus into Praxo: multi-agent retrieval live in production, in-chat presentation generation, and an AI API developer portal of my own creation. I present the architecture to review boards and executive stakeholders.

  4. [act-iv] the discipline

    AI systems engineering

    The current chapter is craft: making AI behave like real software. Shadow-mode validation, feature-flag rollouts, structured outputs, and a 3,000+ test surface. In 2026, Microsoft contracted me directly to help carry an internal AI agent from beta to production; I originated its evaluation platform and authored the readiness assessment behind the rollout. Reliability is the feature that compounds.

[principles]

Operating principles — each with a receipt.

LLMs are components, not systems.
The product is the system around the model: retrieval, routing, validation, rollout. receipt: Praxo's three-tier architecture
Retrieval and reasoning are separate layers.
Each gets its own controls, ranking, and evaluation. receipt: RRF fusion + GraphRAG enrichment layer
No claim without a measurement.
Accuracy, latency, and fallback rates are measured, not assumed. receipt: the numbers on this page — 88%, 32%→0%, +7%/−18%
Ship behind flags, validate in shadow.
Safe rollout beats clever rollout. receipt: Praxo's release path, 8+ feature flags
Architecture is a communication job.
Decisions are logged, presented, and defensible — to engineers and executives alike. receipt: architecture review boards; five-phase migration decision log

[capabilities]

Where I operate.

Architecture & orchestration

Enterprise AI platform architecture · multi-agent systems · domain routing · state machines · phased workflows · SSE streaming

Retrieval & knowledge

RAG · GraphRAG · hybrid search · Reciprocal Rank Fusion · multi-index retrieval · query analysis · entity resolution · context budgeting

Reliability & delivery

Evaluation harnesses · shadow-mode testing · feature flags · structured outputs · observability · structured logging · pytest · Playwright

Cloud & platform

Azure OpenAI · Azure Functions · Container Apps · Cognitive Search · Cosmos DB · Azure AD · Docker · Bicep · PostgreSQL + pgvector · FastAPI · React/TypeScript · Python

Leadership & communication

Architecture review boards · department-wide code review · stakeholder alignment · decision logging · founder operations · enterprise sales

[next]

I own an enterprise AI platform end to end — architecture, code review, the developer portal your engineers build on.

fits — full-time · staff · principal ai-platform · lead · senior ai-architect

If that's the shape of what you're hiring for, email me.

Greenfield, Massachusetts · last.verified 2026-07-24