The verdict in three sentences
Rebuilding a SaaS platform kept alive by an aging MVP costs between 60,000 and 140,000 EUR in Dublin in 2026, depending on codebase size and debt level. The two painful line items: 12,000 EUR of data migration and 20,000 EUR of multi-tenant refactoring, over a 5 to 8 month project. Done well, a rebuild cuts production incidents by 60% and frees the team to build instead of patch.
Rebuild or keep patching: the debt threshold
Every scale-up hesitates. The decision rule comes down to a few measurable indicators: past certain thresholds, patching costs more than rebuilding.
| Indicator | "Keep patching" zone | "Rebuild" zone |
|---|---|---|
| Time on bugs / total dev | < 20% | > 40% |
| Average lead time for a feature | < 2 wk | > 6 wk |
| Production incidents / month | < 3 | > 8 |
| Developer onboarding | < 1 wk | > 3 wk |
| Test coverage | > 50% | < 20% |
| Infra cost / customer | stable | rising |
As soon as three indicators flip into the red zone, the rebuild pays off: every month of delay adds debt and drives developers away. The most common 2026 trigger is the inability to ship a feature sold to a large client on time.
Breaking down the rebuild budget
A rebuild is not a blind rewrite: you isolate critical modules, migrate in batches and keep the old system running in parallel until switchover. Here is a typical 2026 budget structure.
| Item | Content | Cost (EUR) |
|---|---|---|
| Audit & target architecture | Debt mapping, migration plan | 8,000 - 14,000 |
| Multi-tenant refactor | Data isolation, per-client scaling | 18,000 - 24,000 |
| Core module rewrite | 2-3 critical modules | 25,000 - 45,000 |
| Data migration | Scripts, verification, switchover | 10,000 - 15,000 |
| Tests & CI/CD | Coverage, pipeline, monitoring | 8,000 - 16,000 |
| Support & switchover | Dual run, training, rollback | 6,000 - 12,000 |
The low end (60,000 EUR) is a partial rebuild targeting multi-tenant and one module; the high end (140,000 EUR) a rewrite of most of the core with heavy migration. Always avoid the "big bang": a gradual switchover limits the risk of service outage.
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Mini case study
Mark, CTO of a SaaS scale-up in Dublin (HR SaaS, 140 customers, 9 developers), spends 45% of his team's time on bugs and takes 7 weeks to ship a feature. Two large prospects worth 30,000 EUR/year of ARR are blocked by the single-tenant architecture.
He launches a rebuild at 95,000 EUR over 6 months (audit, multi-tenant refactor, rewrite of 2 modules, migration). Target result: time on bugs down to 18%, i.e. about 1.2 developers freed full-time, valued at 90,000 EUR/year. By unblocking the two prospects (60,000 EUR of ARR) and saving dev time, the investment is amortized in under 14 months, excluding lower churn from improved stability.
FAQ
How do we know whether to rebuild rather than patch? Measure the time-on-bugs ratio, feature lead time and incident count. If three of these indicators are in the red zone, the rebuild pays off.
Why does multi-tenant cost 20,000 EUR? Cleanly isolating each customer's data and handling scaling and security touches the core of the architecture. It's the most sensitive item but the one that unlocks enterprise sales.
Can you rebuild without service interruption? Yes, via a gradual switchover (dual run): the old and new systems coexist while customers are migrated in batches. This avoids any risky "big bang".
How much does data migration cost? Between 10,000 and 15,000 EUR depending on volume and how clean the existing model is. It includes scripts, integrity checks and a rollback plan.
How long does a rebuild take? Between 5 and 8 months for a mid-sized scale-up. We deliver in batches to show value by month 2 or 3, rather than waiting until the end.
Let's scope your project. Send us your debt indicators (time on bugs, feature lead time, incidents) and the number of customers to migrate, and we'll frame a gradual rebuild over 5-8 months. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
