Custom Software · Fixed Price

Custom software solutions, delivered at a fixed price

You get one clear scope, one clear price, and a working solution handed over to your team. No open-ended hourly bills — just the result you agreed on.

Fixed price, agreed upfront Reviews at every milestone Clean handover included
How I work

A predictable path from idea to handover

Every project follows the same clear stages, so you always know what happens next and what you are paying for.

1

Intake

We start by getting the requirements sharp and the scope agreed.

  • Talk with stakeholders to determine scope and requirements
2

Environment setup

Everything is prepared so development can start without friction.

  • Set up the development and test environments
  • Arrange the required accounts and access
3

Roadmap presentation

You see the full plan before a line of production code is written.

  • A clear roadmap presented and agreed with you
4

Development with reviews

Development runs in a focused period with checkpoints along the way.

  • In-between reviews to verify the result matches expectations
  • Adjust early instead of at the end
5

Handover

The solution is transferred cleanly — to your team, your company, or hosting arranged by me.

  • Handover to your team or company
  • Or hosting taken care of by me
Backend solutions

What I build

Focused backend engineering that connects systems, moves data, and makes platforms work together reliably.

Middleware

Reliable layers that let your systems talk to each other and exchange data cleanly.

CMS

Content management setups and integrations tailored to how your team actually works.

Adapters & integrations

Custom adapters and connectors that bridge APIs, services and legacy systems.

Data & platform migration

Moving data and systems safely — including platform upgrades (e.g. Java 8 to 21) and on-premise to cloud migrations, with validation so nothing gets lost.

E-commerce

Backends and integrations for shops: catalogs, orders, payments and fulfilment flows.

File conversions

Converting files between formats reliably and at scale, automated end to end.

File transformations

Transforming, enriching and reshaping data files to fit the target system exactly.

High-performance solutions

Event-driven architecture with Kafka and tuned, high-throughput backends built for speed and scale.

Code & architecture reviews

A sharp analysis of your current codebase and architecture, a clear report, and an actionable plan — ideal before an acquisition or a cloud migration.

Workflow orchestration

Durable, long-running business processes built with Temporal — reliable workflows that survive failures, retries and restarts without losing state.

Technology

The stack I deliver with

Proven, modern tooling across backend and frontend — with automated testing and an AI-assisted workflow built in.

Java React Angular Docker Cloud JavaScript TypeScript Kafka (event-driven) Temporal (workflows) High-performance solutions Automated testing AI environment (Claude) for teams

Technologies & expertise

Languages

Java 7–21 · JavaScript · TypeScript · Groovy · Python · Bash · HTML · CSS / SCSS

Frameworks

Spring Boot · Angular · React · Hibernate · Intershop · JUnit · Mockito

Databases

Oracle · MS SQL Server · MySQL · PostgreSQL · PL/SQL

Cloud & servers

Google Cloud · AWS · Azure · Kubernetes · Tomcat · NGINX · Apache

DevOps & build

Docker · Kubernetes · Maven · Gradle · Jenkins · Nexus · Git · Selenium

Methods

REST · SOAP · TDD · Event-driven · SOLID · Agile · Scrum · Lean

Also available

Pre-work for your development team

Not every engagement is a full build. Sometimes a team just needs the groundwork done properly first: requirements clarified, a solution shaped, and ready-to-pick-up tickets. I prepare exactly that, then hand it over so your developers can hit the ground running.

Discuss pre-work

How the pre-work runs

1
Discuss requirements Get the goals, constraints and scope clear with your stakeholders.
2
Solution & roadmap Design the solution and a roadmap, broken down into Jira tickets ready to develop.
3
Handover to the team Transfer everything to your team so they can start building with full context.
Portfolio

Clients I've delivered for

A selection of organisations whose teams and platforms I've built and delivered software for.

Coop Supermarkt
Novamedia
Wolters Kluwer UK
Nederlandse Spoorwegen
Royal IHC
Vanderlande
RAI Amsterdam
Free Your Mind Festival
Fluiconnecto
Flamco
Dynapac
Recommendations

What people I've worked with say

Recommendations shared by colleagues and managers I've worked with directly.

A source of inspiration, not just a senior developer

When we went looking for an extra developer, Jack walked right through the door. A first impression I'll never forget — but one that paled beside the impression his work left on me. Jack is able, like no one else, to carry a team. His personality complements his craftsmanship more than perfectly. Instead of a "normal" senior developer, we got a source of inspiration — someone who brought in good ideas and actually delivered them, again and again finding smart solutions just outside the expected path, yet adding so much value that an enormous amount of future work was saved. I'm glad I got to work with him!
JB
Joost van den Biggelaar IT Manager · managed Jack directly · Aug 2024

Adding value to the journey

After our previous lead developer left, we spent a week figuratively tearing our hair out — that's how good he was. Who would lead the team now? Enter Jack. This all-rounder turned out to be a heavy hitter. At RAI Amsterdam we were building an environment where an exhibitor can arrange almost everything for taking part in an event — from a single bottle of cola at a specific time to complete stands. The diversity of our products brings a lot of complexity, and it's exactly in solving complex problems in a seemingly simple way that Jack feels like a fish in water. He gives you the confidence that however complex the problem, you can reach a good solution with his help. Jack the team player is every bit the equal of Jack the developer. As a Product Owner I learned a lot again about applying Scrum, and he gave me excellent advice in complex situations — which is how we managed to deliver so much functionality. Thanks, Jack!
CO
Cristo Ortega Product Owner · worked with Jack in the same team · Apr 2020
Fixed price

One scope. One price. A finished solution.

For companies that want a defined solution delivered and handed over — start to finish, with the price agreed before development begins.

Agreed scopeDefined together at intake
Fixed priceKnown before we start
Full handoverTo your team or hosting
Request a quote
Contact

Let's scope your project

Tell me what you need built. I'll come back with the scope, the approach, and a fixed price.

Reach me directly

Prefer email or a quick call? Use the details below, or send the form and I'll reply.

Emailjack.duin@am-solutions.nl
Schedule a callAdd your booking link here
Based inThe Netherlands · working remotely

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