The verdict in three sentences
A three-year-old business application costs 15 to 20 % of its build cost every year in application maintenance, otherwise technical debt gets paid in incidents. In Copenhagen in 2026, that means a retainer of 15,000 to 60,000 DKK per month or time and materials at 5,200 to 7,500 DKK per day (700 to 1,000 EUR). The first point to negotiate is not the day rate but the response SLA (4 hours or next business day) and the number of days included for Node and PHP upgrades.
What application maintenance covers in 2026
An application built in 2023 is reaching the age where its technical building blocks expire. Node.js 20 has been out of maintenance since 30 April 2026, PHP 8.1 since 31 December 2025, and PHP 8.2 will receive no security fixes after 31 December 2026. An unmaintained app keeps working until a vulnerable dependency or a browser update breaks it, and for companies in scope of NIS2, unpatched software is also a compliance issue.
| Type of maintenance | Content | Share of annual budget | Concrete example |
|---|---|---|---|
| Corrective | Fixing reported defects | 25 to 35 % | Wrong discount calculation on some orders |
| Preventive and security | Dependency updates, vulnerability patches | 15 to 20 % | Security advisory on an npm library |
| Adaptive | Node, PHP, framework and database upgrades | 20 to 30 % | Moving from Node 20 to Node 22 or 24 |
| Evolutive | Small functional changes | 20 to 35 % | New field, new accounting export |
| Operations | Monitoring, backups, hosting | 5 to 10 % | Restore tested every quarter |
Contract models and their prices
| Model | 2026 price | Days included per month | Response SLA | Fits |
|---|---|---|---|---|
| Time and materials, no commitment | 5,200 to 7,500 DKK per day | As needed | None guaranteed | Low-criticality app, variable budget |
| Prepaid hour bank | 40 hours for 28,000 to 40,000 DKK | Free use over 12 months | 2 business days | Few incidents |
| Essential retainer | 15,000 DKK per month | 2.5 days | Next business day | Internal app, under 50 users |
| Standard retainer | 30,000 DKK per month | 5 days | 4 business hours for blockers, next day otherwise | App used daily by teams |
| Premium retainer | 60,000 DKK per month | 10 days | 4 hours, on-call and 24/7 monitoring | Critical app, external customers |
Unused days are rarely carried over beyond one quarter: check that clause, as it can weigh up to 20 % of the real cost.
The SLA to demand by severity
| Priority | Definition | Response | Target resolution or workaround |
|---|---|---|---|
| P1 blocker | App unavailable or invoicing impossible | 4 business hours | 1 business day |
| P2 major | Key function degraded, workaround possible | Next business day | 3 business days |
| P3 minor | Limited nuisance, display, label | 2 business days | Next release |
| P4 change | New request | Scheduled | Per quote or included days |
| Critical security | Published flaw with CVSS score of 9 or more | 24 h | 72 h |
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
An SLA without penalties is only an intention: ask at least for a credit of 5 to 10 % of the monthly fee in case of repeated breaches.
Mini case study
Mette, CIO of a mid-sized logistics company in Copenhagen, must budget maintenance for a warehouse application built three years ago for 1,200,000 DKK. History shows 12 incidents a year, two upgrades ahead and about 15 days of enhancements, or 35 days of work. On time and materials at 6,000 DKK, that is 210,000 DKK with no guaranteed response. With the Essential retainer (180,000 DKK for 30 days) plus 5 extra days (30,000 DKK), she pays the same 210,000 DKK a year, or 17.5 % of the build cost, but with a contractual next-day SLA. A single day of downtime for 40 warehouse staff at 350 DKK per hour over an 8-hour shift already costs 112,000 DKK.
FAQ
Why 15 to 20 % of build cost per year? It is the observed order of magnitude for keeping an app secure and current: around 10 % for fixes and security, the rest for upgrades and small enhancements. Below 10 %, technical debt piles up.
Can maintenance go to a different provider than the original developer? Yes, with a 2 to 4 week handover phase, typically 40,000 to 90,000 DKK, to take over code, documentation and access.
Is a Node or PHP upgrade included? In a Standard or Premium retainer, usually yes, within the included days. A major framework upgrade can take 5 to 15 days.
How do we measure maintenance quality? Track SLA compliance, reopened incidents and dependency age each month. A one-page monthly report is enough.
What commitment length should we accept? Twelve months renewable with 3 months' notice is the 2026 standard. Avoid 36-month commitments without a review clause.
Let's scope your project. Describe your application, its stack and usage, and we will propose a maintenance model with SLA, included days and a monthly budget. 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.
