Head of Architecture | C# / .NET | Legacy Decomposition | Azure

This is an exclusive role to Optimal, and a brand-new, high-impact hire for an established, profitable UK software business running a mission-critical, high-volume transactional platform that processes billions of transactions in a regulated environment.

You will be the senior-most individual contributor in the engineering function and the person accountable for technical coherence across the whole platform. Your job is to stand up the architecture function from scratch: the target architecture, the ARB process, the Architecture Guild, and the engineering standards that shape how the whole org builds.

This is not a line-management role, and it is not a hands-on feature-development role. It is the technical authority the engineering teams unify behind - a practitioner who reads code, joins design sessions, and gets standards adopted through influence, not command. The function already has strong Principal Engineers, Tech Leads, and a Principal Security Engineer. Your job is to channel that capability into one coherent direction.

Key Responsibilities

• Define and maintain a living 12-24 month target architecture: what stays, what moves, when, and what the service boundaries are
• Build the ARB process - templates, cadence, and the culture where decisions are recorded, traceable, and asked for rather than worked around
• Run the Architecture Guild as your channel for driving standards into teams that do not report to you
• Sequence decomposition: a principled backlog of which parts of the monolith to tackle first, in what order, and why
• Drive the pivot from infrastructure-level monitoring to outcome-based SLOs (latency, error rate, user impact)
• Partner with the Principal Security Engineer on technical security posture
• Publish engineering standards - coding conventions, integration patterns, observability, cross-service contracts - developed with the senior engineers so they reflect real practice
• Support technical hiring: calibration, interview panels, and shaping the technical bar

Eligibility:No sponsorship - you must hold a British passport or Indefinite Leave to Remain (ILR)

Requirement:Seeking a senior architect or principal-level professional with a proven track record of breaking down complex legacy platforms.Must have a solid background in Azure and C#/.NET,no exceptions.

??Non-Negotiables- Please only apply if you have ALL of the following ??

Core Technologies:

• C# and .NET (Framework and modern)
• SQL Server at scale
• Azure (cloud experience essential)
• RabbitMQ, Redis, CI/CD
• Able to read any part of a large codebase to understand what it does (you will not write production features day-to-day)

Environment:

• Significant experience as a senior architect or principal engineer on a complex, multi-year platform - not greenfield
• Proven experience evolving a live system under delivery pressure
• Hands-on with gradual decomposition of legacy systems: strangler patterns, service boundary definition, data migration sequencing
• Experience operating in a regulated environment (PCI DSS, ISO 27001, Cyber Essentials or equivalent)
• Proven ability to influence without authority - you have driven standards adoption across teams that did not report to you

Key Skills:

• Ability to point to a forum, guild, or chapter model you have run and the outcomes it produced
• Strong written and verbal communication across registers - whiteboard with engineers, plain-language summary with commercial stakeholders
• Experience mentoring and growing senior engineers so their judgement develops under your influence, not their dependency on you
• Comfortable defining engineering standards, integration patterns, and cross-service contracts that reflect real practice, * Experience in regulated, payments-adjacent, or similarly compliance-heavy product domains
• Defining and driving an SLO-based observability posture across multiple services
• Hands-on microservices / AKS / Kubernetes at production scale
• Architecture certification (TOGAF, Azure Solutions Architect, or equivalent)
• Background in AppSec or secure design review

If you tick all of the above and you thrive on influence over authority, we would love to hear from you.