# BugFyx > BugFyx is the software company of Patrick Willemsen from ’s-Hertogenbosch, the Netherlands. I maintain and secure apps built with AI, for example with Lovable, Bolt.new, v0, Replit, Cursor or Claude: I fix bugs, close security holes and take care of hosting, database, monitoring and backups. I also build custom SaaS and web apps: projects start at €5,000, and you get a fixed price up front. You always work with me directly, with fixed prices and response times in writing. ## About - BugFyx B.V., Siloweg 3, 5222 BN ’s-Hertogenbosch, the Netherlands. Chamber of Commerce (KvK) number: 85781517. VAT number: NL863739842B01. - Owner: Patrick Willemsen, full-stack software engineer with 8+ years of experience at companies such as ING, ABN AMRO and de Volksbank. BSc ICT & Software Engineering, Fontys University of Applied Sciences, Eindhoven (2021). Works in Dutch and English. - BugFyx has worked for ING, ABN AMRO, de Volksbank, VodafoneZiggo and TCS. Insured for professional liability. - Contact: patrickwillemsen@bugfyx.nl, +31 6 34988015 (also WhatsApp). LinkedIn: https://www.linkedin.com/in/patrick-willemsen. Contact form: https://bugfyx.nl/en/contact/. - Clients are served across the Netherlands and abroad, mostly remotely, and in person in the ’s-Hertogenbosch (Den Bosch) area. ## Who BugFyx is for For founders without a technical background who built an app with AI, for small and medium-sized businesses with an internal tool they made themselves or with AI, and for start-ups with a new app that is going to market. What they have in common: the app works, but they want someone who takes care of security, database and hosting and can be reached when something goes wrong. Apps built with Lovable, Bolt.new, v0, Replit, Cursor and Claude are taken over and maintained, in React, Next.js, TypeScript, Supabase, Firebase, Node.js, Python, Java, Spring Boot, PostgreSQL and Vue. ## App Check A fixed-price inspection of an app built with AI: €600 excluding VAT, for 1 app with up to 15 screens or pages, 1 database and up to 3 connections to other services. Bigger apps get a fixed quote first. See https://bugfyx.nl/en/app-check/. - Secret keys: API keys and passwords that are visible in the code or in the browser. - Database and permissions: Whether users only see their own data, for example with Row Level Security in Supabase or the rules in Firebase. - Sign-in and access: Whether sign-in, password reset and admin pages are properly protected. - Outdated packages: Packages with known vulnerabilities (CVEs) and updates that have been waiting for a long time. - Hosting and backups: Where your app runs, whether there are backups and whether you can restore them. - Code and stability: Errors, slow pages and code that will fall over with the next change. The result is a plain-language report with every risk ranked red, orange or green, and a 30-minute walkthrough call, within 5 working days. If a maintenance plan starts within 30 days, the full €600 is deducted from the plan. BugFyx does not carry out formal penetration tests. ## Maintenance plans Monthly plans, cancellable every month with a notice period of one month. Prices exclude VAT. See https://bugfyx.nl/en/ai-app-maintenance/ and https://bugfyx.nl/en/pricing/. - Basic: €600 per month, 5 support hours a month. Support by Email (reply within 1 working day). For a stable app that needs a fix now and then. - Plus: €1,100 per month, 10 support hours a month. Support by Email (reply within 1 working day) and WhatsApp (reply within 4 hours). For an app with paying users that keeps growing. - Business: €2,050 per month, 20 support hours a month. Support by Email (reply within 1 working day), WhatsApp (reply within 4 hours) and Phone (answered or called back within 1 hour). For an app your business runs on. Every plan includes: monitoring of your app, day and night; daily checks for known vulnerabilities (CVEs) and updates; backups and protection of your data; management of hosting and database; bug fixes, small changes and advice. Response times, the same in every plan: - Outage: your app is down. Within 2 hours. On working days between 9:00 and 17:00. - Serious incident at the weekend. Within 4 hours. Saturday and Sunday. - A bug that doesn’t stop your work. Picked up the next working day. On working days. Extra hours cost €100 an hour one-off, or €80 an hour (20% off) when added to a plan every month. ## Custom software Custom SaaS platforms and web apps, built with Java, Spring Boot, PostgreSQL, Vue and TypeScript. Projects start at €5,000 excluding VAT, and every project gets a fixed price up front. No mobile apps or desktop software. See https://bugfyx.nl/en/custom-software/. - SaaS platforms: Software your customers pay for every month, with accounts, roles and payments. - Internal tools: Your own system instead of spreadsheets, for planning, administration or reporting. - Customer portals: A place where your customers view their data, upload documents or track orders themselves. - Integrations: APIs and integrations between your systems, so data no longer has to be copied by hand. Example: Traecy (https://traecy.nl), Patrick Willemsen’s own SaaS for quality management in food & feed, built since 2025 with Java, Spring Boot, PostgreSQL, Vue 3 and TypeScript and used by 7 companies: Willemsen Kip, TM Salades, Habo Vlees, Compagnon Culinair, Buswhisky, Van Oers Foodservice and Châteraisé Europe. See https://bugfyx.nl/en/custom-software/traecy/. ## Experience - ABN AMRO (2026 – now), Java software engineer: New applications through the whole development cycle: designing and building APIs, writing tests, deploying through CI/CD and monitoring in production. - TCS (2025 – 2026), Lead AI integration engineer and Java software engineer: Built an app with large language models end to end, and turned an outdated system that processes more than 100,000 invoices a year into tested Java services. - ING (2022 · 2024 – 2025), Java software engineer: Features and bug fixes for InsideBusiness, ING’s wholesale banking platform, helped recover the application after incidents, and built ESG reports for regulators. - Benerail (2023 – 2024), Lead Java software engineer and scrum master: An API following the OSDM standard that lets travel agents worldwide book European rail travel, in a team of two. - VodafoneZiggo (2021 – 2022), Full-stack software engineer, through FrontWave: Maintenance and new features for a CMS running more than 80 web shops, where downtime during peak traffic is not an option. - de Volksbank (2020 – 2021), Java integration specialist: Spring Boot integrations between the bank’s COBOL systems and the software of mortgage advisers, including CI/CD and coaching a junior developer. ## Guides - [Is your Lovable, Bolt or v0 app secure? 10 things to check](https://bugfyx.nl/en/guides/secure-ai-built-app/): Your app works and your first customers are logging in. But is it secure? These ten checks show where AI-built apps leak most often, and what to do about it. - [Supabase Row Level Security explained for founders](https://bugfyx.nl/en/guides/supabase-row-level-security/): If your app runs on Supabase, Row Level Security decides who may see which data. Here is how it works in plain language, how to check that it is set up right and which mistakes you want to avoid. - [Launching your AI-built app: a checklist for hosting, backups and monitoring](https://bugfyx.nl/en/guides/ai-app-launch-checklist/): What to sort out before real users rely on your app: your own accounts, separate environments, backups that work, monitoring, email that arrives and GDPR. - [Vibe coding: when do you need a real developer?](https://bugfyx.nl/en/guides/vibe-coding-when-to-hire-a-developer/): Vibe coding gets you from idea to working app fast. Here is when you need a developer alongside it, what they actually do and how to hand your app over. - [What does web app maintenance cost in 2026?](https://bugfyx.nl/en/guides/web-app-maintenance-costs/): What you pay for every month once your web app is live, what pushes the price up or down and what to check before you sign a maintenance contract. - [Having custom SaaS built: costs, timelines and pitfalls](https://bugfyx.nl/en/guides/custom-saas-development-costs/): What a first version should contain, what drives the price, how a good project runs and which mistakes cost you money and time along the way. ## Frequently asked questions ### What is BugFyx? BugFyx is the software company of Patrick Willemsen from ’s-Hertogenbosch, the Netherlands. I maintain and secure apps built with AI, for example with Lovable, Bolt.new, v0, Replit, Cursor or Claude: I fix bugs, close security holes and take care of hosting, database, monitoring and backups. I also build custom SaaS and web apps: projects start at €5,000, and you get a fixed price up front. You always work with me directly, with fixed prices and response times in writing. ### Who is BugFyx for? For founders without a technical background who built an app with AI, for small and medium-sized businesses with an internal tool they made themselves or with AI, and for start-ups with a new app that is going to market. What they have in common: the app works, but they want someone who takes care of security, database and hosting and can be reached when something goes wrong. ### Which AI tools and technology do you work with? I take over apps built with Lovable, Bolt.new, v0, Replit, Cursor, Claude or another AI tool. The technology underneath is usually React, Next.js or Vue with TypeScript, and a database in Supabase, Firebase or PostgreSQL. Node.js, Python, Java and Spring Boot are familiar ground too. ### Where is BugFyx based, and do you work remotely? BugFyx is based at Siloweg 3 in ’s-Hertogenbosch, the Netherlands. I work for clients across the Netherlands and abroad, mostly remotely. If you are in the Den Bosch area, we can also meet in person. ### Do you work in Dutch and English? Yes. I work in Dutch and English, and I explain technical matters without jargon. ### What is the App Check? The App Check is an inspection of your app for a fixed price of €600 excl. VAT. I check security, database, hosting, backups, outdated packages and code quality. Within 5 working days you get a plain-language report with the risks ranked red, orange and green, and we go through it together in 30 minutes. ### Does my app fit in the App Check? The fixed price covers one app with up to 15 screens or pages, one database and up to 3 connections to other services, such as payments, email or signing in with Google. Simply count the screens you can open in your app, such as sign-in, dashboard and settings. If your app is bigger, you get a fixed quote first. ### What happens to the €600 if I take a maintenance plan afterwards? If you start a maintenance plan within 30 days of the App Check, I deduct the full €600 from your plan. The App Check then costs you nothing extra. ### What do you need from me for the App Check? Access to the code, for example through GitHub, and read access to your hosting and database, such as Supabase, Firebase or Vercel. Plus a short explanation of what your app does and who uses it. I help you share that access. ### Do you fix the problems during the App Check? The App Check is the inspection and the report. What needs fixing, I pick up afterwards: within the support hours of your maintenance plan, or separately for €100 an hour. You choose what gets fixed. ### What is included in a maintenance plan? Every plan includes monitoring of your app, a daily check for known vulnerabilities (CVEs) with the matching updates, backups and protection of your data, management of hosting and database, and a fixed number of support hours a month for bug fixes, small changes and advice. Basic has 5 hours, Plus 10 hours with WhatsApp, Business 20 hours with WhatsApp and phone. ### How fast do you respond when my app is down? For an outage I respond within 2 hours, on working days between 9:00 and 17:00. For a serious incident at the weekend within 4 hours. A bug that does not stop your work, I pick up the next working day. These times apply in every plan. Because your app is monitored, I often get an alert before you notice. ### What if I need more hours than my plan includes? One-off extra hours cost €100 an hour. If you need more hours every month, you add them to your plan for €80 an hour, a 20% discount. ### How long am I tied to a maintenance plan? Not long: every plan can be cancelled monthly, with a notice period of one month. ### Can I keep building my app with AI myself? Yes. You can keep building with Lovable, Cursor or another tool. I keep an eye on what changes, and if a new version breaks something or opens a hole, I fix it. ### Do you do penetration tests? No. I do not carry out formal penetration tests or issue pentest reports. If you need one for a certification or a client’s requirement, a specialised firm is the right party. With the App Check and maintenance, I make sure your app goes into that well prepared. ### What exactly do you do for security? I check whether secret keys are out of the code, whether your database only shows what a user is allowed to see, for example with Row Level Security in Supabase, and whether sign-in and permissions work properly. Every day I check your app’s packages for known vulnerabilities (CVEs) and update them. And I take care of backups and well-protected access to your data. ### Do you help with the GDPR? On the technical side, yes: I make sure your app protects personal data properly, with restricted access, encrypted connections and backups. I do not give legal advice on the GDPR, such as your privacy statement or data processing agreements. ### What kind of custom software do you build? SaaS platforms, web apps, internal tools, customer portals and integrations between systems. Everything runs in the browser. I do not build mobile apps for the App Store and Google Play, or desktop software. ### How does the fixed price for custom software work? We first decide together what the first version needs to do. Then you get a fixed price for exactly that version, so you know the cost up front. Projects start at €5,000 excl. VAT. I build in short rounds and show you what is there along the way, so you can steer. ### Which technology do you build custom software with? With Java and Spring Boot for the backend, PostgreSQL as the database and Vue with TypeScript for the front end. Proven technology that banks use too and that many developers know. My own SaaS Traecy runs on it as well. ### Do the prices include VAT? No, all prices on this site exclude VAT. ### What does work outside a plan cost? One-off hours cost €100 an hour excl. VAT. For bigger jobs and custom software you get a fixed price up front. ### Which maintenance plan suits me? Basic suits a stable app that needs a fix now and then. Plus suits an app with paying users that keeps growing, and gives you WhatsApp for quick questions. Business is for an app your business runs on, with phone availability within an hour. After the App Check I give you advice. ## Pages - [Home](https://bugfyx.nl/en/), in Dutch: [Home](https://bugfyx.nl/nl/) - [Maintenance](https://bugfyx.nl/en/ai-app-maintenance/), in Dutch: [Onderhoud](https://bugfyx.nl/nl/onderhoud-ai-apps/) - [App Check](https://bugfyx.nl/en/app-check/), in Dutch: [App Check](https://bugfyx.nl/nl/app-check/) - [Security](https://bugfyx.nl/en/security/), in Dutch: [Beveiliging](https://bugfyx.nl/nl/beveiliging/) - [Custom software](https://bugfyx.nl/en/custom-software/), in Dutch: [Maatwerk](https://bugfyx.nl/nl/maatwerk-software/) - [Traecy case](https://bugfyx.nl/en/custom-software/traecy/), in Dutch: [Case Traecy](https://bugfyx.nl/nl/maatwerk-software/traecy/) - [Pricing](https://bugfyx.nl/en/pricing/), in Dutch: [Prijzen](https://bugfyx.nl/nl/prijzen/) - [About me](https://bugfyx.nl/en/about/), in Dutch: [Over mij](https://bugfyx.nl/nl/over-mij/) - [Den Bosch](https://bugfyx.nl/en/software-developer-den-bosch/), in Dutch: [Den Bosch](https://bugfyx.nl/nl/software-ontwikkelaar-den-bosch/) - [FAQ](https://bugfyx.nl/en/faq/), in Dutch: [Veelgestelde vragen](https://bugfyx.nl/nl/veelgestelde-vragen/) - [Contact](https://bugfyx.nl/en/contact/), in Dutch: [Contact](https://bugfyx.nl/nl/contact/) - [Guides](https://bugfyx.nl/en/guides/), in Dutch: [Kennisbank](https://bugfyx.nl/nl/kennisbank/) - [Securing AI apps](https://bugfyx.nl/en/guides/secure-ai-built-app/), in Dutch: [AI-app beveiligen](https://bugfyx.nl/nl/kennisbank/ai-app-beveiligen/) - [Supabase RLS](https://bugfyx.nl/en/guides/supabase-row-level-security/), in Dutch: [Supabase RLS](https://bugfyx.nl/nl/kennisbank/supabase-row-level-security/) - [Launching](https://bugfyx.nl/en/guides/ai-app-launch-checklist/), in Dutch: [Live gaan](https://bugfyx.nl/nl/kennisbank/ai-app-live-zetten-checklist/) - [Maintenance costs](https://bugfyx.nl/en/guides/web-app-maintenance-costs/), in Dutch: [Kosten onderhoud](https://bugfyx.nl/nl/kennisbank/kosten-onderhoud-webapp/) - [Vibe coding](https://bugfyx.nl/en/guides/vibe-coding-when-to-hire-a-developer/), in Dutch: [Vibe coding](https://bugfyx.nl/nl/kennisbank/vibe-coding-developer-nodig/) - [Custom SaaS](https://bugfyx.nl/en/guides/custom-saas-development-costs/), in Dutch: [Maatwerk SaaS](https://bugfyx.nl/nl/kennisbank/maatwerk-saas-laten-bouwen/) - [Terms and conditions](https://bugfyx.nl/en/terms/), in Dutch: [Algemene voorwaarden](https://bugfyx.nl/nl/algemene-voorwaarden/) - [Privacy statement](https://bugfyx.nl/en/privacy/), in Dutch: [Privacyverklaring](https://bugfyx.nl/nl/privacyverklaring/)