AI-native software product development · Named professional accountability

Turn a business need into
a working software product.

Q: What types of companies does AP4 Digital work with?

We work with mid-sized and large companies, as well as organisations building digital products, that need a business-critical web, mobile, AI or enterprise solution designed, integrated and brought into live operation.

Q: Does this make development faster?

The aim of AI-native delivery is to shorten feedback cycles by accelerating repetitive, readily verifiable tasks and to leave more team capacity for genuine product value. We do not claim a guaranteed multiplier or cycle-time advantage in advance; with an approved baseline, we measure the actual effect through cycle time, accepted output, rework and post-release defects.

Q: Does AI write all the code?

No. AI may support analysis, code drafts, refactoring, testing and documentation, but a human professional remains accountable for architecture, critical business logic, security, code review and release decisions.

Q: How much does a custom software product cost?

Custom development typically starts from €13k net. The realistic range depends on scope, integrations, migration, security and validation; when the scope is uncertain, product discovery is the right place to start. For substantially smaller work (under €2.5k) a freelancer serves you better, and for multi-team programmes above €250k an enterprise integrator is the better choice.

Q: How long does it take to deliver the first version?

A well-defined first version can often be delivered in 4–17 weeks. With complex integrations, migration or a regulated environment, the programme is divided into multiple stages that can each be accepted independently.

Q: How fast do I get a quote?

After a 30-minute call you get a first professional opinion and a preliminary scope with time and budget ranges within 2 business days. The detailed, committed proposal (technical design, team composition, milestones, fixed or T&M pricing) follows after discovery.

Q: What if we don’t have a precise specification yet?

Most of our clients arrive with a 2–3 page idea outline or the pain points of an existing system, that is exactly why we have the product discovery phase. Within 1–3 weeks we reach a prioritised scope and the decision gates, and from there fixed pricing can be given.

Q: Who owns the source code and documentation?

The client receives the project's source code and the necessary documentation in line with the handover terms defined in the contract. Licences, third-party components and handover conditions are agreed at the start of the project. There is no vendor lock-in: any other team can take the delivered system forward.

Q: What happens to our data and codebase?

We use enterprise AI subscriptions with EU data residency and zero-data-retention. The client codebase and data never enter the training sets of public models. If a self-hosted LLM is required, we handle that too (Mistral, Llama, on-prem deployment).

We design and build web and mobile software products, enterprise platforms and AI solutions, from business goal to live operation. As an AI-native product team, we use AI for verifiable work across analysis, design, engineering, testing and documentation, while named professionals remain accountable for architecture, critical code, security and release.

AI-native delivery - a standard tool, not an experiment
Named architecture and code review - a named owner
Source code and documentation - handover fixed in the contract

Discuss your product with us Featured case studies

Brief professional discussion · no obligation · NDA welcome

Rodin's Thinker holding a phone - bronze statue

100+

Successful projects

13+

Industries

50+

Mobile apps

8+ yrs

Avg. experience

Independent reviews

Clutch

View profile →

How we work: 5 steps

Business problemWe map the need and the measurable goals.

AI-accelerated designPrototype and architecture in days.

Development & integrationA working system connected to your environment.

Senior controlCode review, QA, security and performance.

Measurable resultsA live system: faster, more transparent operations.

Lead timeManual hoursError rateWe agree the metrics and their baselines together in the first phase.Live systemStable operations, measurable business value

Free · 30 minutes · no obligation

A free assessment. Within 2 business days: your preliminary proposal.

A structured assessment, a first professional opinion, a preliminary scope with budget range: the detailed proposal follows after discovery. If we are not the right partner, we will tell you.

Your call will be taken by
Ákos Boka · Head of Sales

Book a 30-minute call ↗

Brief professional discussion · no obligation · NDA welcome

Prefer email? hello@ap4.hu

A definition, in one paragraph

What does AI-native software product development mean?

At AP4 Digital, AI-native software product development is a delivery model in which AI is a standard tool for verifiable work across analysis, design, engineering, testing and documentation. Named professionals remain accountable for the business goal, product priorities, architecture, critical code, security and production release.

The aim is a shorter feedback cycle: We use AI to support clearly defined parts of research, specification, prototyping, implementation drafts, test cases, code review and documentation, so demonstrable results are ready for decisions sooner.
More capacity for product value: We accelerate repetitive, readily verifiable work with machine assistance so the team can devote more attention to business logic, product decisions, integrations and user value.
Quality is not delegated to a model: Named professionals review the architecture, critical business logic, security decisions, code and release. AI supports delivery; accountability remains with the AP4 team.

In short

A delivery model in which AI is a standard tool for verifiable work across analysis, design, engineering, testing and documentation. Named professionals stay accountable for architecture, critical code, security and release.

The team · Why AP4? · B2B software · Budapest · since 2013

The speed of specialists. The accountability of a stable product partner.

We work as an established, multi-disciplinary product team with direct professional accountability, short feedback cycles and end-to-end product-development ownership.

What sets us apart

AI does not replace the senior expert. It speeds up the repetitive parts of design, development, testing and documentation, while business and technical decisions stay with senior engineers.

Actual speed-up depends on project maturity, specification quality and integration complexity.

Our leaders

4 leaders · 25+ experts

Dienes IstvánProjekttervezés és vezetői minőségbiztosítás

Sárközi AndrásOperatív működésért felelős vezető · senior business analyst és projektvezető

Boka ÁkosÉrtékesítési vezető

Víg DávidOperatív vezető

Senior decision-makersWe never delegate technical decisions to juniors.

Safe AI usageYour code and business data never enter public training pipelines.

Fixed milestonesPre-defined deliverables, costs and decision points.

Owner-level oversightEvery project is supervised by a senior lead, up to owner level.

Research-based methodologyOur risk framework for AI-assisted development is built on published literature and real-world project experience.

Fixed price, fixed deadlineA fixed price and deadline for each phase, no surprise invoices at the end of the quarter.

25+Experts

8+ yrsAvg. experience · min. 5 yrs

100%Hungary-based contracting party

100+Delivered projects · 13+ industries

AI summary · What AI search cites

AP4 Digital is a Budapest-based software product development partner. It designs and builds web and mobile products, enterprise platforms and AI solutions from real business problems. Projects are led by senior engineers, AI tooling is used under control, and delivery closes with documented handover and clear ownership terms.

30-minute conversation

Which business situations can we help with?

A new digital product

There is a business goal and a market opportunity, but the product concept, scope and route to delivery still need to be clarified.

Product discovery and prototype

A stalled system or one that is difficult to evolve

Technical debt, slow changes or integrations constrain operations and growth.

Legacy system modernisation

A mobile customer or employee experience

The business process requires frequent use, device capabilities, offline operation or an app-store presence.

Mobile application development

A process that may benefit from AI

The data, risk, expected value and route to a working pilot need to be assessed against a specific business goal.

Enterprise AI and readiness

Solutions

The right solution depends on the nature of the problem.

We do not sell one product for every situation. Which direction is right is determined by the current system, the data and the decision at hand.

03 · Entry point

Product discovery

A basis for decisions, a prioritised scope and realistic time and cost ranges before committing to development.

Product framingPrototypePrioritised scopeTime and cost range

€5–13k · 1–3 weeksDetails

Our most common engagement · 01

Custom software development

Web-based business systems, portals and integrations when standard software no longer fits the process.

Frontend · React · React Native · TypeScriptBackend · Node · Python · GoData · PostgreSQL · Redis · Vector DBInfra · AWS · GCP · Azure

from €13k4–17 weeksDetails

02 · Mobile

Mobile application development

iOS and Android products from the first product decision through app-store release and continued development.

Swift · KotlinReact NativeApp Store · PlayOffline-first

from €15–38k · 6–14 weeksDetails

04 · Modernisation

Legacy modernisation

Retain, refactor, replatform, partially replace or rewrite within a controlled decision framework.

Kotlin · Swift · Java.NET · PHPStrangler figTest rebuild

from €15–20k · 4–39 weeksDetails

05 · Built on your data

Enterprise AI

Audit, readiness, pilot and production integration tied to a measurable business goal, with defined data-processing and operating conditions.

Rapid AI AuditPrivate RAGLLM pipeline · MLOpsEU data residency

from €3.8k + VAT · from 5 business daysDetails

06 · Enterprise platform

Tailored ERP

A modular system built around the process and data model, starting with a 10-business-day System Design Sprint.

System Design SprintModular ERPProcess and data modelIntegrations

from HUF 690k + VAT · 10 business days (sprint)Details

References · 30 projects

Not presentations: live business systems.

6 featured projects, more on the References page.

TMRW Hotels - digital guest experience and mobile product. BKK Telebusz - an app supporting a travel and service process.

Every case study states the starting situation, the solution delivered, the type of result and - where publishable - how it was measured. If a result is not public, we say so.

FeaturedTourism · Mobile app · 2025

Process

A transparent path from the first decision to live operation.

First decision

no - we refine, then retry

Product framing

Output: brief

Is the goal clear?

yes

Prototype and validation

Output: prototype

Validated?

yes

Development and launch

Output: release

Ready for production?

yes

Measurement and evolution

Output: roadmap

prioritised roadmap → next iteration

AI accelerates

Summarising research and market analysis

Structuring requirements

User story drafts

AI accelerates

Rapid UI variant generation

A prototype within hours

Evaluating feedback

AI accelerates

AI-assisted coding with senior review

Automated test generation

Documentation drafting

AI accelerates

Analysing usage data

Faster support responses

Roadmap prioritisation suggestions

Live product

continuous measurement and support

First decision

Product framing

Output: brief

Summarising research and market analysis · Structuring requirements · User story drafts

Is the goal clear? yes ↓ · no ↺ previous phase

Prototype and validation

Output: prototype

Rapid UI variant generation · A prototype within hours · Evaluating feedback

Validated? yes ↓ · no ↺ previous phase

Development and launch

Output: release

AI-assisted coding with senior review · Automated test generation · Documentation drafting

Ready for production? yes ↓ · no ↺ previous phase

Measurement and evolution

Output: roadmap

Analysing usage data · Faster support responses · Roadmap prioritisation suggestions

prioritised roadmap → next iteration

Live product

continuous measurement and support

Discuss your product with us The full six-stage process with decision gates →

decision gate - we only proceed on a yes

Verified operating facts.

AI-native delivery, named professional accountability and shared quality gates from the business goal to production release.

We publish business facts only from approved sources.

Facts and figures · process details

Human decision gates

business goal
product priority
architecture
security
code review
release

A named professional is accountable for each one. AI supports delivery; accountability remains with the AP4 team.

Facts and figures · 8 facts Structured fact sheet for press, partners and procurement

Company: AP4 Digital - a brand of Cell-Line IT Security Kft. · Budapest · since 2013
Team: 25+ senior-capacity team · 4–8 per project · senior-led
Industries: 13+ industries · HU · EU · GB
Timelines: PoC 1–3 weeks · custom software 4–17 weeks · legacy 4–39 weeks
Pricing: PoC €5–13k · custom software from €13k · retainer from €750/month
Compliance: ISO 27001 and ISO 9001 certified operations · EU AI Act, GDPR, NIS2 · SonarCloud A · A · A
Billing: Hungarian Kft. · HUF / EUR / GBP accepted · intra-EU reverse-charge VAT.
Languages: Hungarian and English

What cost and time ranges should you expect?

PoC (Proof of Concept)

€5–13k

1–3 weeks · fixed price

The entry point: a fast, fixed-fee decision milestone.

Custom software development

from €13k

4–17 weeks · fixed scope or T&M

The most common engagement: a custom business system with integrations.

Complex production mobile app

from €50–125k

12–26 weeks

A complex mobile product through to its first production release.

Rapid AI Audit

from €3.8k + VAT

5 working days

An assessment of AI opportunities at a fixed price, in 5 business days.

The exact range depends on scope, integrations, data quality, security requirements and validation needs.

Every range, cost driver and pricing model in one place: pricing and project costs →

12 questions

FAQ.

* frequently asked questions

Frequently asked questions.

Still have a question? Email hello@ap4.hu, we reply within 2 business days.