01
Operable system map
Components, dependencies, risk zones, interfaces and potential rupture points. You finally know what you are deciding on.
IS modernisation
Make the existing system evolve without breaking operations. — progressive modernisation of architectures in production and integration of new capabilities
Your systems in production carry your business. Controlled coexistence between the old and the new, progressive integration of new capabilities, releases by stages: a trajectory piloted from diagnosis to operation.
Symptoms
When a system starts drifting.
Every release becomes a source of stress
Manual verification grows, dependencies are blurred, no one wants to touch critical zones any more.
You must open the system without being able to rewrite it
API, cloud, new channel or new service : the existing system must hold while you transform it.
Debt slows every evolution
Today's workaround becomes tomorrow's risk. Cycles stretch, arbitrations freeze.
The system's memory is leaving
The people who know the system are leaving. Documentation didn't keep up. Opacity becomes structural.
Intervention discipline
Strangler Pattern
Isolate before replacing. We wrap the legacy system, isolate critical components and replace brick by brick. The existing system runs while the new takes shape.
Software archaeology
Understand before touching. COBOL, legacy Java, forgotten PHP : AI accelerates the redocumentation of orphan code, the extraction of buried business rules, the identification of real opacity zones.
Production milestones
Advance through regular production releases, short feedback loops. Operational continuity is a design constraint, not a secondary goal. No tunnel effect, no risky switchover.
Impact analysis
Never decide blind. Documentation kept current, traceability by default, no blind spot on dependencies before any change.
Trajectory
Four milestones, no switchover.
01
Understand the existing system
Risk mapping, regulatory constraints (eIDAS, GDPR, etc.), technical viability validation.
02
Identify rupture points
Target architecture, stack choices, isolation points to protect first, security by design.
03
Transform progressively
Build, automated tests, CI/CD pipelines, controlled production switchover without service interruption.
04
Stabilise over time
Continuous supervision, compliance held, integration of evolutions without loss of mastery. Knowledge transfer to your teams.
BEFORE Common situation
- Coupled monolith Quarterly releases, impossible rollback, paralyzed teams.
- Orphaned code No documentation, turnover = major risk.
- Very long cycles 6 to 12 months between each major evolution.
- Fragile dependencies Every change can break something elsewhere.
AFTER With REELIANT
- Modular architecture Strangler Pattern, tier-by-tier migration, no interruption.
- Living documentation AI used to re-document and map existing code.
- Continuous CI/CD Daily deploys, automated tests, 1-click rollback.
- Full observability Structured logs, metrics, real-time distributed traces.
What we deliver
Useful deliverables, not an audit that sleeps in a folder.
02
Target trajectory and prioritisation
A staged transformation plan, with sequencing, risks, preconditions and explicit arbitrations.
03
Realistic first execution lot
A concrete scope to launch quickly, small enough to reduce risk, useful enough to produce a visible effect.
04
Takeover and maintenance framework
Architecture standards, documentation, tests and checkpoints so that debt does not rebuild at the next lot.
Proof in production
Comparable cases, already taken over or transformed.
When modernisation touches a system in production, evidence beats promises.
Public Finance & Asset Management
Modernisation of the FRR Extranet - French Pension Reserve Fund
Extranet used by the FRR's partner asset managers to submit their daily, weekly and monthly financial reports. REELIANT was already running the application maintenance on the legacy platform hosted by Informatique CDC, before taking over its full maintenance and modernisation. The constraint: no reporting cycle could be interrupted during the transition.
- no process interruption
- daily to monthly reporting
- next-day on-site SLA
Finance & mortgage guarantees
Modernisation of the Crelog.com banking extranet - Crédit Logement
Banking extranet and web APIs Crelog.com used by more than 200 partner banks of Crédit Logement to process guaranteed property transactions at scale. A core business system, modernised without breaking service. Urbanisation, continuous integration, cybersecurity, high availability and 24/7 managed operations addressed in parallel, not in sequence.
- 500,000 guaranteed transactions per year
- 200 partner banks
- 500,000 lines of code migrated and restructured
Frequently asked questions.
How do you modernise a legacy system without service interruption?
By applying the strangler pattern: we wrap the existing system, isolate critical components and replace them brick by brick, without any risky switchover. Service continuity is a design constraint, not a secondary goal.
What is the strangler pattern?
A progressive modernisation technique that runs the old and the new system in parallel, gradually routes traffic to new components, and only retires the legacy once the new system is validated in production.
How do you rebuild documentation for an orphan COBOL or legacy codebase?
Through AI-assisted software archaeology : the source code is analysed to extract buried business rules, identify real opacity zones and reconstitute operable documentation. What used to take months of deciphering is reduced to a few days of analysis.
Do you need to rewrite everything to modernise an IS?
No. A full rewrite is the riskiest scenario. We favour successive evolutions with regular production releases, short feedback loops and progressive integration of new capabilities rather than rebuilding.
What do you deliver in a modernisation diagnostic?
A useful diagnostic must allow you to decide. We deliver a real-system map, prioritised risk zones, a target trajectory, a realistic first execution lot and the takeover conditions for your teams.
An existing system to take over?.
Software archaeology, risk mapping, progressive trajectory : we start by understanding before acting.
Diagnose my existing system