Every release has become a risk event
Manual checks multiply, dependencies are unclear and nobody wants to touch the critical parts anymore.
Information System Modernization
Information System Modernization — legacy IT modernization, technical debt reduction and strangler pattern
Your systems carry your critical operations, but they slow your teams down. We modernize without disruption, brick by brick, with a trajectory you control.
The challenge
Why modernizing is so difficult
Technical debt accumulates
Every workaround today becomes tomorrow's risk. Cycles lengthen, changes become frightening.
Change is frightening
The older the code, the higher the perceived risk. Every decision is deferred to avoid breaking everything.
Knowledge evaporates
The people who know the system leave. Documentation hasn't kept up. Opacity becomes structural.
Our 3 invariable principles
No big bang
Successive incremental evolutions. Service continuity is a constraint, not a secondary objective.
No tunnel
Frequent deliveries, continuous feedback. You see progress at every step.
No blind spots
Impact analysis before every change. Documentation kept up to date throughout the project.
Typical trajectory
A progression in 4 steps
01
Audit & mapping
Identify technical debt and real risks. A prioritized, actionable plan within 2 weeks.
02
Trajectory
Preserve what works, isolate critical components, prioritize by business value and quick ROI.
03
Progressive execution
Targeted refactoring, APIsation, Cloud migration. In secured, tested, documented steps. No tunnel.
04
Sustainment
The system transitions into our MCC so technical debt never re-accumulates.
Modernization without service disruption
From opaque architecture to progressive mastery, step by step, no big bang.
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.
When to call us
The signs that a modernization effort should start now
You must open the system without rewriting it
API exposure, cloud migration or a new channel must happen while the existing system keeps carrying the business.
System knowledge is leaving the company
Documentation is thin, business rules are buried in code and the people who understand the whole picture are no longer there.
What we deliver
Deliverables that support execution, not a report that gets archived
01
An actionable map of the real system
Components, dependencies, risk zones, interfaces and likely failure points. You finally know what you are deciding on.
02
A target trajectory and priorities
A transformation plan by batches, with sequence, risks, prerequisites and trade-offs made explicit.
03
A realistic first execution batch
A concrete scope to launch quickly, small enough to reduce risk and large enough to produce a visible result.
04
A sustainment framework for the next steps
Architecture rules, documentation, tests and control points so the next batch does not recreate the same debt.
Method
Two invariants of our approach
Strangler Pattern
We wrap the old system, isolate critical components and replace brick by brick.
Software archaeology
COBOL, legacy Java, forgotten PHP: we use AI to re-document orphaned code, extract buried business rules and identify real blind spots. What once took months of deciphering is reduced to a few days of analysis.
What you gain
Technical debt reduction
Readable architecture, maintainable code, teams that move forward with confidence.
Business continuity
No disruption imposed on your teams or your clients during the migration.
Faster delivery cycles
Frequent releases, short feedback loops, shared progress.
Long-term trajectory
A modernization aligned with your operational constraints over time.
Proof in production
Comparable systems already taken over or transformed
When modernization touches a critical system, proof matters more than positioning.
Public Finance & Asset Management
Modernisation of the FRR Extranet - French Pension Reserve Fund
Takeover and modernisation of the Extranet FRR, used by partner asset managers to submit daily, weekly and monthly financial reports. REELIANT was already handling TMA on the legacy solution hosted by Informatique CDC before taking over full management.
- no process interruption
- daily to monthly reporting
- next-day on-site SLA
Finance & mortgage guarantees
Modernisation of the Crelog.com banking extranet - Crédit Logement
Modernisation of the Crelog.com banking extranet and web APIs for Crédit Logement, used by more than 200 partner banks to process guaranteed property transactions at scale. The project focused on a core business system with simultaneous urbanisation, continuous integration, cybersecurity, high-availability and 24/7 managed operations challenges.
- 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: wrapping the old system, isolating critical components and replacing them brick by brick, with no big bang. Service continuity is a design constraint, not a secondary goal.
What is the strangler pattern?
A progressive modernisation technique that lets old and new systems coexist, gradually routing traffic to new components and retiring the old one only once the new one is validated in production.
How do you reconstruct documentation for orphaned COBOL or legacy code?
Through AI-assisted software archaeology: source code is analysed to extract buried business rules, identify true blind spots and rebuild usable documentation,what normally takes months of deciphering is reduced to a few days of analysis.
Does modernising a system always require a full rewrite?
No. A complete rewrite (big bang) is the riskiest scenario. We favour successive evolutions with regular production releases, short feedback loops and technical debt that decreases with each iteration rather than rebuilding.
What do you actually deliver in a modernization diagnostic?
A useful diagnostic must support a decision. We deliver a map of the real system, the priority risks, a target trajectory, a realistic first execution batch and the conditions for your teams to take the next steps with control.
Got a legacy system to take over?
Software archaeology, risk mapping, progressive trajectory: we start by understanding before we act.
Audit my existing system