The verdict in three sentences
Modernizing a legacy app in Dakar costs between 15M and 45M FCFA in 2026 with a progressive approach, versus 30M to 80M FCFA for a full rewrite. The progressive route (strangler pattern) is almost always right for an SME: it spreads risk and budget across 4 to 9 months without stopping operations. The payoff is maintenance cut by roughly 40% and a sharp drop in production incidents.
Modernization cost by approach in 2026
Inheriting an outdated PHP app means paying invisible technical debt every month: slowness, bugs, no room to evolve. Here are the ranges observed in Dakar (with a Miami benchmark), as a 2026 order of magnitude.
| Line item | 2026 range (FCFA) | Timeline |
|---|---|---|
| Technical audit + mapping | 2M - 5M | 2-4 weeks |
| Progressive rewrite (strangler) | 15M - 45M | 4-8 months |
| Full rewrite (big bang) | 30M - 80M | 6-9 months |
| Data migration | 3M - 10M | 3-6 weeks |
| Post-rewrite maintenance | 0.4M - 1.2M /month | ongoing |
| Internal team training | 1M - 3M | 1-2 weeks |
The upfront audit is non-negotiable: it drives the estimate and prevents nasty surprises in data migration, often the most underestimated item. (As a benchmark, comparable Miami engagements run 2-4x these USD-equivalent figures.)
Progressive rewrite vs big bang
A big bang rewrites everything then switches over at once; the strangler pattern replaces modules one by one, old and new coexisting through the transition.
| Criterion | Progressive rewrite | Big bang |
|---|---|---|
| Total cost | 15M - 45M FCFA | 30M - 80M FCFA |
| Timeline | 4-8 months | 6-9 months |
| Switchover risk | Low (per module) | High (all at once) |
| Service interruption | None to minimal | Possible |
| Return on investment | Gradual | Deferred |
| Best for | SME, critical app | Small or frozen app |
Modernization cuts maintenance by about 40%: fewer fixes, more efficient hosting, faster developers on a modern base. An app costing 1M FCFA/month in maintenance can fall to around 600K FCFA/month, i.e. 4.8M FCFA saved per year.
Mini case study
Mr Ndiaye, CIO of a logistics firm in Dakar (72 staff), inherits a 9-year-old PHP fleet-tracking app: slow, undocumented, with a single developer able to touch it. He opts for a progressive rewrite at 32M FCFA over 7 months, plus 800K FCFA/month maintenance. Maintenance drops from 1.1M to 650K FCFA/month, i.e. 5.4M FCFA saved per year, and incidents halve. The project pays back in about 5 years on maintenance alone, before counting the new features finally possible.
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
FAQ
How much does modernizing a legacy app cost in Dakar in 2026?
Between 15M and 45M FCFA for a progressive rewrite, and 30M to 80M FCFA for a full rewrite. The spread depends on app size, technical debt and the volume of data to migrate.
Should I rewrite everything or modernize in stages?
For an SME with a live app, the progressive route (strangler pattern) is almost always preferable: it spreads risk and budget with no service interruption. Big bang is only justified for a small or frozen app.
How long does modernization take?
From 4 to 8 months progressively, 6 to 9 months for a full rewrite. Data migration adds 3 to 6 weeks and should be tested early to avoid surprises.
What savings should I expect after modernization?
Roughly 40% less maintenance, plus a clear reduction in bugs and development lead times. An app at 1M FCFA/month in maintenance can fall to around 600K FCFA/month.
Does the budget include data migration?
It is often billed separately: 3M to 10M FCFA depending on volume and the quality of the source data. It is the most underestimated item and should be priced during the audit.
Let's scope your project. Tell us about your current app, its technology and your evolution priorities, and we will price the audit then the progressive rewrite. 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.
