Infrastructure security architect

Mission Overview:

Keystone Solutions is seeking an Infrastructure, Security and Architecture allrounder for a consultancy mission with our client, guiding the migration of IT from a Belgian entity to the French headquarters.

Key Responsibilities:

Assessment & migration strategy

• Audit the Belgian IT landscape: infrastructure, applications, identities, licences, contracts, data flows and technical debt.
• Map Belgian systems against French headquarters standards and identify gaps, overlaps and dependencies.
• Define the target architecture and migration approach for each domain (rehost, replatform, consolidate, retire).
• Build the migration roadmap with phases, milestones, cutover windows and rollback plans.
• Prepare the business case, including costs, risks, licence consolidation and expected savings.

Infrastructure & cloud

• Plan and run the migration of servers, storage, virtualization and backup to the headquarters' datacenter or cloud platforms.
• Lead network integration: WAN/SD-WAN interconnection, VPN, DNS, IP addressing, firewalls and site connectivity.
• Run identity consolidation: Active Directory/Entra ID merger and Microsoft 365 tenant-to-tenant migration (mail, Teams, SharePoint, OneDrive).
• Migrate endpoints and device management (Intune/SCCM, MDM) to headquarters tooling with minimal user disruption.
• Make sure monitoring, backup, disaster recovery and business continuity remain covered throughout the transition.

Security & compliance

• Align the Belgian entity with the group's security policies, ISO 27001 controls and security tooling (EDR, SIEM/SOC, IAM, PAM, MFA).
• Run risk assessments before and after each migration wave, and keep the risk register up to date.
• Keep GDPR compliance in place during data transfers, and update records of processing, DPAs and retention rules.
• Handle NIS2 obligations in both jurisdictions, coordinating with the Belgian CCB and the French ANSSI frameworks where relevant.
• Secure the transition period: temporary trust relationships, privileged access, data-in-transit protection and decommissioning of legacy access.
• Make sure Belgian legacy systems are securely wiped and decommissioned, with evidence kept for audit.

Architecture & governance

• Act as design authority for all technical decisions in the integration programme.
• Document as-is and to-be architectures, standards and integration patterns.
• Rationalize the application portfolio and define the future of Belgium-specific tools (HR, payroll, invoicing, local regulatory systems).
• Make sure Belgian legal and operational requirements are preserved in the target solution, such as social secretariat interfaces, local tax and e-invoicing, and language needs (FR/NL).

Stakeholders & vendors

• Act as the main technical link between Belgian management, French headquarters IT, and external partners.
• Manage vendors, integrators and MSPs: contract transitions, termination notices, TSAs and handover of services.
• Report progress, risks and decisions to steering committees.
• Support change management with user communication, training, hypercare after cutover, and service desk alignment.

Knowledge transfer & handover

• Make sure local IT knowledge is documented and transferred to headquarters teams.
• Define the post-migration support model and operational runbooks.
• Hand over to run teams once each workstream is stable, and close the programme with a lessons-learned review.

Required Qualifications and Skills:

• French and English mandatory.
• Able to speak with all stakeholders from teams to C level.
• Comfortable operating under Keystone Solutions' consultancy model, embedded on site or in hybrid mode with the client across Belgian and French entities.

Consultancy Nature of Work:

• Operate as a Keystone Solutions consultant embedded with the client, coordinating efforts across application, infrastructure and security domains to ensure a smooth migration.
• Work on site with client teams when required, collaborating closely with Belgian and French stakeholders to align timelines, risks and change plans.

Dynamic Projects Across Clients:

• Engage in a flagship migration program while building experience that translates to future client engagements, from infrastructure modernization to application lifecycle optimization.
• Leverage exposure to d