AP4 Digital
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AI-native software product development · Named professional accountability

Turn a business need into
a working software product.

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 usFeatured case studies

Brief professional discussion · no obligation · NDA welcome

Rodin's Thinker holding a phone - bronze statue
BKK logoSimplePay by OTP logoÁrukereső.hu logoFashion Street logoEurop Assistance logoPraktiker logoSwiss Clinic logoMagyar Posta logoImperatore Travel World logoRekortan logoZalakaros logoMÉH Zrt. logoArtisjus logoFerro-Sped 2000 logoCool4U Solar logoanet360 logo
C
Independent reviews
Clutch
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100+
Successful projects
13+
Industries
50+
Mobile apps
8+ yrs
Avg. experience
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
Prefer email? hello@ap4.hu

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.
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.

The AP4 Digital senior development teamBudapest · since 2013
Senior decision-makers We never delegate technical decisions to juniors.
Safe AI usage Your code and business data never enter public training pipelines.
Fixed milestones Pre-defined deliverables, costs and decision points.
Owner-level oversight Every project is supervised by a senior lead, up to owner level.
Research-based methodology Our risk framework for AI-assisted development is built on published literature and real-world project experience.
Fixed price, fixed deadline A fixed price and deadline for each phase, no surprise invoices at the end of the quarter.
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.

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.

BKK logoSimplePay by OTP logoPraktiker logoMagyar Posta logoEurop Assistance logo
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.

Our most common engagement 01

Custom software development

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

from €13k4–17 weeksDetailsFrontend React · React Native · TypeScriptBackend Node · Python · GoData PostgreSQL · Redis · Vector DBInfra AWS · GCP · Azure
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-firstfrom €15–38k6–14 weeksDetails
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€5–13k1–3 weeksDetails
04 Modernisation

Legacy modernisation

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

Kotlin · Swift · Java.NET · PHPStrangler figTest rebuildfrom €15–20k4–39 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 residencyfrom €3.8k + VATfrom 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 modelIntegrationsfrom HUF 690k + VAT10 business days (sprint)Details

Not presentations: live business systems.

References · 30 projects

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.

3 featured projects, more on the References page.

Tourism · Mobile app2025

TMRW Hotels mobile app

A complete smart-hotel system: reception, room key and concierge in a single mobile app, from booking to check-out.

Case study
Education · Web development2025

Black Cell

Gamified e-learning platform for mandatory cybersecurity training: points, badges and leaderboards keep employees motivated.

Case study
Logistics · ERP2024

MÉH-SYS ERP

Waste management ERP: inter-site material flow, weighbridge integration and invoicing in a single system.

Case study
View all 30 references

A transparent path from the first decision to live operation.

  1. Clarify

    Business goal, user, risk and decision context.

  2. Design

    Scope, UX, architecture and acceptance criteria.

  3. Deliver

    Short iterations, regular demos and visible decisions.

  4. Launch and measure

    Controlled release, documentation, support and the next roadmap decision.

The full six-stage process with decision gates

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.

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.

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.
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 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.
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.
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.
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.
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.
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.
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.
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).
Handover is not the end of the relationship: on a monthly retainer (from €750/month) we handle operations, bug fixes and further development, with a written SLA. The retainer is a monthly budget, whatever a given month does not use for fixes can be reallocated to development.
AP4 provides an established, multi-disciplinary product team and organisational continuity, while decisions remain directly with the professionals doing the work. This combines the speed of specialists with the end-to-end accountability of a stable partner.

All 30 questions in one place: full FAQ →

Do you have a business problem or product idea that needs clear decision and delivery ownership?

Brief professional discussion · no obligation · NDA welcome

In the initial discussion, we will clarify the goal, the main risk and the realistic next step.

Answers to common questions before the call: FAQ →

What you will get
01
During the 30 minutes
A problem & fit assessment. Under NDA if needed.
02
First
A first professional opinion by email: direction, risks, suggested next step.
03
Within 2 business days
A preliminary scope with time & budget range, in writing.
04
After discovery
A detailed, committed proposal: design, milestones, pricing.
05
Either way
A second opinion on your plan, even if we are not the right partner.
Or describe it briefly
We send a preliminary time & budget range within 2 business days.

* Required field

We use your data solely to get in touch: privacy policy
Structured fact sheet (for press, partners and procurement)

Company: AP4 Digital is a brand of Cell-Line IT Security Kft. · Budapest · since 2013

Size: 25+ senior-capacity team · 4–8 people/project · senior-led

Expertise: Software product development (web + mobile), enterprise platforms, legacy modernisation, RAG/MLOps, AI audits

Industries: B2B SaaS, fintech, healthtech, industrial, logistics

Typical turnaround: PoC 1–3 weeks · Custom software 4–17 weeks · Legacy rewrite 4–39 weeks

Pricing: PoC €5–13k · custom software from €13k · MLOps/RAG from €13k · legacy rewrite from €15–20k · retainer from €750/month

Compliance: EU AI Act, GDPR and NIS2 aspects handled in the delivery process · SonarCloud A·A·A · enterprise AI subscription with zero-data-retention settings

Stack: React, React Native, TypeScript, Node, Python, Go, PostgreSQL, AWS/GCP/Azure, LangChain, Anthropic Claude, OpenAI

Invoicing: Hungarian Kft. · HUF / EUR / GBP accepted · intra-EU reverse-charge VAT. Prices updated: 2026-08-05.