The verdict in three sentences
A legacy application (PHP/jQuery, accumulated technical debt) eventually costs more to maintain than to modernise: bugs, downtime and security flaws stack up. In 2026, a replatforming runs between 60,000 and 200,000 EUR over 5 to 10 months, with data migration at 15-25% of budget. The right call is not technical but economic: compare the annual cost of debt with the cost of migration.
Rehost, replatform, rewrite compared
The three modernisation strategies, 2026 orders of magnitude.
| Strategy | Principle | 2026 cost (EUR) | Timeline | Risk |
|---|---|---|---|---|
| Rehost | Move as-is (cloud) | 15,000 - 40,000 | 1-3 months | Low |
| Replatform | Modernise in batches | 60,000 - 200,000 | 5-10 months | Medium |
| Rewrite | Rebuild from scratch | 150,000 - 400,000+ | 10-18 months | High |
Incremental refactor vs full rewrite
| Criterion | Incremental refactor | Full rewrite |
|---|---|---|
| Business continuity | Preserved | At risk |
| Total cost | Medium | High |
| Value return | Fast, in batches | Late |
| Data migration | Staged | Big-bang |
| Recommended if | Critical app in prod | Unmanageable debt |
Cost items and data migration
| Item | Share of budget | Comment |
|---|---|---|
| Framing + architecture | 8-12% | Mapping, targets |
| Development | 45-55% | Core of migration |
| Data migration | 15-25% | Cleaning, mapping, tests |
| Testing + QA | 12-18% | Non-regression |
| Cutover + training | 5-10% | Deployment, change mgmt |
Risk / value matrix
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| Module | Business value | Technical debt | Priority |
|---|---|---|---|
| Billing | High | High | 1 (urgent) |
| Catalogue | High | Medium | 2 |
| Reporting | Medium | High | 3 |
| Internal admin | Low | High | 4 |
| Static pages | Low | Low | 5 (later) |
Mini case study
Mr Ferrando, CIO of a distribution SME in Dublin, runs a 2015 PHP application that crashes 2 to 3 times a month. Each incident consumes 1.5 person-days and causes a half-day of stopped order intake, i.e. an estimated 3,200 EUR/month of technical debt, roughly 38,400 EUR/year. An incremental replatforming at 110,000 EUR over 8 months, starting with the billing module (priority 1), eliminates critical incidents by the 3rd month. With the annual debt of 38,400 EUR gone, the migration pays back in a little under 3 years, before counting the security gain and the end of commercial interruptions.
FAQ
How much does a legacy migration cost in 2026? A replatforming sits between 60,000 and 200,000 EUR; a simple cloud rehost starts at 15,000 EUR, a full rewrite often exceeds 150,000 EUR.
Do I need to rewrite everything? Rarely: incremental refactoring in batches preserves activity and delivers value sooner; a rewrite is only justified when debt is unmanageable.
How much does data migration cost? Budget 15 to 25% of the total: it is the most underestimated item, spanning cleaning, mapping and consistency testing.
How long does it take? A full replatforming takes 5 to 10 months depending on module count and data-migration complexity.
How do I avoid business disruption? By working in batches with a temporary dual run: the old and new applications coexist while each module is validated.
Let's scope your project. Describe your current application (technology, modules, incident frequency) and target budget; we'll propose a priced rehost/replatform/rewrite strategy and a zero-downtime cutover plan. 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.
