Architecture Strategy & Roadmaps
Target-state architecture and multi-year roadmaps for data centre, network and security estates, tied to business outcomes and built for four-nines resilience.
Independent practice · Taking on engagements
Infrastructure, thought through.
I'm Sean O'Brien, a network and security architect and engineering leader with 15+ years across financial markets, global enterprise and cloud. I've engineered ultra‑low‑latency trading infrastructure, led distributed network and IT security teams across time zones, and built Zero Trust architectures. Now I help organisations set direction, make the hard architecture calls and lead the teams that deliver infrastructure that is fast, secure and built to last.
- OSCPOffensive Security
- AWSSolutions Architect
- BEngQueen's Belfast
- 日本語Professional
Built infrastructure at
- CME Group
- IMC Trading
- Rapid7
- Capita
- Fujitsu
01Services
Architecture for systems where every packet matters.
Senior architecture and leadership, from strategy and design authority to building the team that delivers it. Your engineers or partners do the build; I make sure it's the right build.
Design Authority & Reviews
Independent review and sign-off of designs before they're built, then assurance through delivery so the result matches the intent. Includes an attacker's-eye view (OSCP).
Zero Trust & Security Architecture
Segmentation strategy, Layer 7 controls and SASE: from evaluation and proof of concept to a phased programme your teams can execute.
Fractional & Interim Leadership
A part-time Head of Network & Security: direction, standards, hiring and mentoring, and a team that's trusted across the business.
Vendor Selection & Due Diligence
Vendor-neutral technology evaluations, RFPs and proofs of concept, plus technical due diligence for investment and M&A. The right solution, not the familiar one.
Specialist Advisory
Low-latency trading and exchange connectivity, automation and infrastructure-as-code strategy, and the GPU networking that AI infrastructure demands.
15+
years engineering networks across three countries
~99.99%
availability across global network & VPN services
~95%
reduction in network build times through automation
6 yrs
in financial markets: exchange & ultra-low-latency trading
02Approach
Senior thinking, without the layers.
You work directly with the architect, not a sales layer. I set direction, make the hard design calls and guide your team or delivery partners through implementation, so nothing gets lost between the strategy and the switch.
-
01
Understand
Business, risk, latency and operational requirements first. No boxes get drawn until the problem is clear.
-
02
Architect
Designs that balance resilience, security, performance and cost, documented so they survive contact with reality.
-
03
Guide
Design authority through the build: reviewing, unblocking and keeping delivery true to the design, whoever's at the keyboard.
-
04
Enable
Standards, runbooks and knowledge transfer so your team owns the result with confidence.
Ways to engage
Architecture Review
A focused, fixed-scope assessment of your network and security architecture, ending in a prioritised roadmap.
Design Authority
I own the architecture; your engineers or integration partner build it. Reviews, decisions and sign-off from design to cutover.
Fractional Leadership
A part-time Head of Network & Security or Lead Architect, embedded with your teams for months, not weeks.
Advisory & Due Diligence
Vendor and technology evaluations, proofs of concept and technical due diligence you can act on.
03Experience
Eighteen years, eight hops.
From Japan to Amsterdam to Belfast: exchanges, trading floors, managed services and a global security company. Select a hop for detail.
$ traceroute --career sean-obrien
-
- Built network and application monitoring with Nagios and GroundWork.
- Designed, built and tested enterprise networks: routing, switching, load balancing, SSL VPN, AAA.
- Hands-on with Cisco and Juniper; technical consultancy across infrastructure projects.
- Bridged Japanese engineering teams and international partners across language and culture.
-
- Engineered BGP connectivity between global cloud environments.
- Linux and Windows, Xen virtualisation, storage (RAID, iSCSI, NAS), virtual firewalls and load balancing.
- Developed automated monitoring configuration tooling.
- Took part in international platform deployments and global release integration.
-
- Low-latency networks supporting globally distributed trading and market data.
- Multicast market data platforms carrying high-volume exchange data.
- Load balancing, content delivery and high-availability services; exposure to InfiniBand.
- Business-critical production where availability and rapid fault isolation were non-negotiable.
-
- Designed and ran ultra-low-latency trading infrastructure across Europe, with connectivity to major exchanges including the London Stock Exchange, Deutsche Börse and NYSE.
- Bespoke architectures on specialist hardware where latency, jitter and determinism were the business.
- Built internal monitoring and performance tooling with Prometheus, sFlow, Grafana and MongoDB.
- Worked side by side with traders and developers to turn trading requirements into designs.
-
- Customer-facing network and security architecture for large organisations.
- Cisco VXLAN-based private cloud networking and scalable data centre design.
- Routing, switching, segmentation, firewalls and secure, cloud-connected environments.
- Balanced resilience, security, performance and commercial constraints with customers and vendors.
-
- Created and led a multi-year global network redesign across office, data centre and lab.
- Replaced the global physical firewall estate with a platform built for Zero Trust.
- Introduced automation that cut network build times by ~95%.
- Hardened isolation for development and security research environments, including Metasploit.
- Rebuilt the Network Engineering function and grew engineers into senior roles.
-
- Led Network Engineering and IT Security while staying hands on in architecture.
- Multi-year data centre roadmaps with VXLAN and eBGP; ~99.99% availability across network and VPN.
- Led Zero Trust and SASE design, evaluation and a successful proof of concept.
- Infrastructure as code with Panorama, CloudVision and Terraform; MCP tooling for AI-driven infra queries.
- Vulnerability management, ASM, CAASM, PKI, DLP, email security and VPN modernisation; worked with CISO and CTO.
-
- Everything above, available to your organisation directly.
- Architecture strategy, design authority and fractional leadership, plus the AI infrastructure that comes next.
- Start a conversation →
✓ destination reached
- BGP
- VXLAN / EVPN
- Multicast
- Spine-leaf
- Arista
- Cisco
- Juniper
- Palo Alto
- Panorama
- CloudVision
- Terraform
- AWS
- Linux
- Zero Trust
- SASE
- Segmentation
- PKI
- InfiniBand
- GPU networking
- Prometheus
- Grafana
- sFlow
- MCP
- CAASM
- Load balancing
- High availability
04Leadership
The architect is also the leader.
I've led network engineering and IT security teams from the UK for a US-headquartered company, worked directly with CISO and CTO-level stakeholders, and grown engineers into senior roles. When you bring me in, you get both the design and the leadership to deliver it.
-
Distributed teams
Trust, accountability and real camaraderie across time zones. Remote teams that feel supported and stay focused on the bigger picture.
-
Vendor-neutral
The right solution for the business, not the most familiar one. Vendors are evaluated on a level playing field and run as true partnerships.
-
People first
I champion my team's work, invest in their careers and grow engineers into senior technical and leadership roles.
-
Vision to roadmap
I turn strategy into feasible implementation roadmaps and bring security to the table early, with thorough contingency planning.
“Sean is the all too rare breed of IT leader who lives at the intersection of vision, intellect, and pragmatism.”
“Managing distributed technical teams from the UK for a US-headquartered company isn't easy, but Sean makes it look effortless. He creates a culture of trust, accountability, and genuine camaraderie across time zones.”
“Sean is the rare manager who pairs deep technical and architectural expertise with genuine advocacy for his team. … I would jump at the chance to work with him again.”
“Sean was always focused on identifying the right solution for the business rather than simply selecting the most familiar option. … He helped bring together technical teams, business stakeholders, and vendors.”
Excerpts from LinkedIn recommendations. Read them in full →
05About
Where deep architecture meets business strategy.
My foundation is high-performance, low-latency networking. Six years in financial markets, first on global exchange and market data infrastructure at CME Group, then engineering ultra-low-latency trading systems at IMC in Amsterdam, taught me to design for environments where latency, jitter and resilience have direct commercial impact.
I've since broadened that into network, security and infrastructure architecture at scale: leading Network Engineering and IT Security at Rapid7, building multi-year data centre roadmaps, replacing a global firewall estate and taking Zero Trust and SASE from concept to proof.
Today I'm most interested in programmable infrastructure, bringing network platforms, infrastructure state and source of truth together, and in the AI infrastructure and GPU networking that builds on everything above.
日本での勤務経験があり、日本語でのご相談も承ります。
Worked in Japan for four years. Consultations in Japanese are welcome.
# cogito-consultancy.com
name: Sean O'Brien
role: Founder & Principal Architect
base: United Kingdom
works: globally, remote & on-site
engagements: advisory · design authority · fractional
certifications:
- OSCP
- AWS Solutions Architect (Associate)
education: BEng Electronic & Software Eng.
# Queen's University Belfast
languages:
en: native
ja: professional
es: elementary
strongest_at: architecture × leadership × strategy
status: available