Your legacy SaaS deserves better than technical debt.
Zero-downtime migration, modern frontend rewrite, optimised backend and CI/CD in place. We modernise your stack without rebuilding everything from scratch.
Modernise without breaking everything. It's possible.
Most SaaS rewrites fail because they try to rebuild everything at once. Six months of parallel development, a risky migration and users seeing no change for months: that is the scenario we avoid.
Our approach is incremental: we audit the technical debt, prioritise the biggest gains, and migrate component by component with zero downtime. The result: a modern, maintainable, scalable application with 91% less technical debt.
6 levers for a modern, maintainable SaaS.
Full technical audit
Mapping of technical debt, circular dependencies, security vulnerabilities, performance issues. Prioritised report with effort estimates.
Data migration
Zero-downtime migration from your legacy database to PostgreSQL/Supabase. 100% of data preserved, validated in staging.
Frontend rewrite
Migration from legacy Angular/Vue.js to Next.js 14, React 18. Bundle divided by 13, LCP under 1.5s, Lighthouse 90+.
Backend optimisation
Rewrite of critical endpoints in Node.js 20. API P95 from 840ms to 95ms. Modern REST architecture, typed with TypeScript.
CI/CD & DevOps
GitHub Actions, automated tests, review apps and deployment in 3 minutes. No more risky manual deployments.
Training & handover
Complete technical documentation, 4h team training session, pair programming and code review for 1 month after delivery.
Every metric, before and after.
Our migration dashboard tracks the modernisation progress in real time: technical debt, performance, test coverage and overall application health.
- Detailed technical audit report with prioritisation
- Zero-downtime migration validated in staging
- LCP under 1.5s and JavaScript bundle divided by 13
- API P95 reduced from 840ms to 95ms
- Test coverage rising from 8% to 78%
- CI/CD with 3-minute deployment
- Technical documentation and team training included
4 phases for a risk-free migration in 10 weeks.
Audit & Strategy
Complete technical debt mapping, migration risk analysis, prioritisation order and sprint planning.
- Technical debt report
- Dependency mapping
- Migration roadmap
- Effort estimate per module
Data & infra migration
Zero-downtime migration from the legacy database to Supabase/PostgreSQL, with full validation in a staging environment before switchover.
- Staging DB migration validated
- Rollback scripts
- Regression tests
- Zero-downtime data go-live
Frontend & backend rewrite
Component-by-component migration of the Angular/Vue frontend to Next.js, rewrite of critical backend endpoints and automated test implementation.
- Next.js 14 frontend
- Typed Node.js 20 API
- 78% unit test coverage
- GitHub Actions CI/CD
Go-live & Training
Final production migration, load testing, post-migration monitoring and team training session on the new architecture.
- Final production release
- Load tests validated
- Datadog/Sentry monitoring
- Team training 4h
Your questions about legacy SaaS modernisation.
Tout ce que vous voulez savoir avant de moderniser votre SaaS avec nous.
Yes, that is our guarantee. We use a progressive migration approach: each component is validated in staging before being switched to production. Database migration uses double-write techniques that allow instant rollback if needed.
Rarely. We start with an audit that identifies the 20% of code causing 80% of problems. We prioritise critical parts: performance bottlenecks, security vulnerabilities and the hardest-to-maintain modules. The rest is refactored progressively.
Between 6 and 12 weeks depending on your SaaS complexity. Standard applications (50,000 to 200,000 lines) are migrated in 10 weeks. SaaS with many third-party integrations or very large databases may need 3 to 4 months.
100%. We systematically validate the data migration in staging with a full set of anonymised production data. The production switchover only happens after complete validation. If something goes wrong, rollback scripts restore the previous state in under 5 minutes.
That is the goal. We deliver complete technical documentation, the architecture diagram, ADRs (Architecture Decision Records) and a 4h team training session. One month of post-delivery pair programming is included to ease the handover.
On average our clients see: -60% infrastructure costs (lighter bundle, fewer servers), -40% developer time on bugs (less technical debt), +35% conversion rate (10x performance) and significantly reduced security risk.
Your legacy SaaS modernised in 10 weeks. Zero downtime.
Free technical audit of your application, prioritised report and migration roadmap. We tell you exactly what is slowing your SaaS down.
Our complementary expertise