Principal Enterprise (C#.NET) Architect

Collinwood is assisting our client in their effort to hire/engage an experienced C#.NET Architect. In this role, you will be the lead architect on this engagement. You will own the technical analysis and all architecture deliverables (a Product Owner handles the product and business requirements side).
Note: This role can either be a full-time salary or a long-term contractor

WHAT YOU'LL DO

● Profile and assess codebases using AI-assisted tooling; validate existing architecture documentation (C4 diagrams) against live code; identify gaps and discrepancies.

● Evaluate a modular monolith architecture direction: assess whether module boundaries are enforced in code or aspirational, and validate the pattern against scalability goals.

● Design batch processing architecture for scale: parallel processing model, partitioning strategy, and infrastructure sizing.

● Assess third-party integration patterns: synchronous vs. asynchronous call patterns, file transfer modernization, and design an integration architecture that holds at scale.

● Validate security and identity architecture: consolidation path to a centralized identity model with role-based access control.

● Define a North Star architecture (long-term vision) and a first-milestone target architecture (what gets built now), ensuring near-term decisions don't foreclose future initiatives.

● Produce an execution-ready roadmap: phased implementation plan, workstream sequencing with dependencies and critical path, staffing plan with trade-off options, and a directional cost model.

● Deliver an in-person executive readout presenting architecture, roadmap, and cost estimate to client leadership.

WHAT WE NEED FROM YOU

● Deep experience leading enterprise architecture for platform modernization engagements — not just designing systems, but producing the artifacts that let a client move into execution (roadmaps, staffing plans, cost models, Gantt charts).

● Strong hands-on background in C# / .NET. You need to evaluate an existing C# codebase and design the future state, not just draw boxes.

● Working familiarity with Python/Django — enough to assess a legacy monolith codebase, identify coupling patterns, and understand what needs to be decomposed.

● Experience with modular monolith patterns: module boundary definition, internal contracts between modules, data ownership, and decomposition strategies.

● Experience designing batch processing systems at scale — job orchestration, parallel execution, database partitioning, lock contention management.

● Familiarity with third-party integration architecture — async messaging patterns, retry/circuit breaker design, file transfer modernization (FTP-heavy environments).

● Security and identity architecture experience — centralized auth (Azure AD preferred), RBAC design, audit logging.

● C4 diagramming fluency. Read, annotate, and produce C4 diagrams without a learning curve.

● Comfort working alongside a strong client-side architect with informed opinions. Collaborative peer, not prescriptive. Validate, challenge where warranted, and extend.

● Executive-level communication skills. Present architecture and cost recommendations to C-suite stakeholders.

● Ability to operate at speed. Use AI-assisted tooling to compress codebase analysis and reserve your time for the architectural judgment calls.

NICE TO HAVE

● Financial services or insurance domain experience.

● Experience with AI-assisted development workflows (Cursor, Claude Code, or similar).

● Experience producing directional cost models for large-scale modernization programs.

● On-premise infrastructure experience.