The verdict in three sentences
In Berlin in 2026, modernizing a legacy app (aging PHP, technical debt) costs between 75,000 and 190,000 EUR depending on scope, over 6 to 12 months. The right method is not a big bang but the strangler pattern: rewrite in batches, never cutting off the service. The real comparison is not "rebuild vs nothing" but rebuild vs the rising cost of the status quo (outages, security holes, climbing maintenance).
The hidden cost of the status quo
A legacy app is not free: it costs more every year. The line items pile up silently until the major incident hits.
| Item (status quo) | Estimated annual impact |
|---|---|
| Maintenance on debt | 27,000-55,000 EUR |
| Outages / downtime | 11,000-45,000 EUR |
| Security risk (unpatched CVEs) | High / unquantifiable |
| Obsolete hosting overhead | 5,000-16,000 EUR |
| Lost team productivity | 16,000-32,000 EUR |
| Inability to evolve | Opportunity cost |
Added up, these often exceed 65,000 EUR/year — the price of a partial modernization amortized in 18-24 months.
The 2026 modernization budget
The strangler pattern replaces the old system module by module. You keep the app in production and gradually redirect traffic to the new services.
| Item | Timeline | Indicative cost |
|---|---|---|
| Technical audit + mapping | 2-3 wks | 9,000-16,000 EUR |
| Modern foundation (auth, CI/CD) | 4-6 wks | 16,000-27,000 EUR |
| Data migration | 3-6 wks | 13,000-32,000 EUR |
| Batch rewrite (strangler) | 4-8 months | 32,000-95,000 EUR |
| Testing, cutover, docs | 3-5 wks | 11,000-22,000 EUR |
After the rebuild, maintenance drops 30-50 % thanks to a tested, documented, debt-free codebase.
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Mini case study
Karim, CTO of a logistics SME in Berlin, inherits a 2014 PHP app: 40,000 EUR/year of maintenance, two major outages last year (~23,000 EUR loss), and a critical unpatchable CVE. The status quo costs him about 70,000 EUR/year.
He launches a batch modernization at 148,000 EUR over 9 months, with no service interruption. Post-rebuild, maintenance falls to 21,000 EUR/year (-47 %) and outages disappear. Annual saving: ~49,000 EUR. The investment amortizes in ~3 years, and above all he regains the ability to ship new features — impossible before.
FAQ
What does a legacy rebuild cost in 2026? Between 75,000 and 190,000 EUR depending on app size, data volume and the number of modules to rewrite.
Should I rebuild everything at once? No: the strangler pattern rewrites in batches without cutting service, reducing risk and spreading the investment.
How long does it take? From 6 to 12 months by scope; the first modernized modules often ship in 2-3 months.
What is the gain after the rebuild? Maintenance drops 30-50 %, outages fall and the ability to evolve is restored.
What about data migration? Plan 13,000 to 32,000 EUR depending on volume and data quality; never underestimate this line item.
Let's scope your project. Share your current stack, indicative budget and timeline, and we'll frame a batch modernization with zero downtime. 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.
