Web applications, mobile apps and business tools for companies in La Rioja and across Spain. You talk directly to the person writing the code, from idea to production.
From a web application to the tool your team will use every day.
Business software and internal tools built around the way you work: bookings, inventory, orders, reporting. No paying for what you don’t use.
Customer portals, admin dashboards and apps that live in the browser. Fast, accessible and easy to maintain.
iOS and Android apps from a single codebase, with a polished experience on every screen.
I connect your tools, APIs and databases so information flows on its own and repetitive tasks disappear.
Not sure which one fits?Tell me and we’ll figure it out
I get to know your business, your users and the real problem before writing a single line of code.
I propose the solution, the scope and a clear plan with fixed timelines and budget.
I work in short iterations and show you real progress, so you decide on something tangible.
I launch, train your team and stay by your side with maintenance and improvements.
The first conversation is free and with no commitment.
In person in Logroño or over a video call.
Besides client work, MJ Devs builds its own products.
Live
Work-hour records for small businesses
Your team clocks in from their phone with one tap and the company manages everything from a web panel: schedules, requests and reports.
Got a product idea or a tool you’re missing?Tell me about it
MJ Devs is the studio of Javier Carreño, a software developer based in Logroño, Spain. I design and build web applications, apps and business tools for small companies, shops and professionals in La Rioja and across Spain.
No middlemen: you always talk to the person writing the code.
Technologies I work with
I am based in Logroño and meet clients in person in La Rioja and nearby. With the rest of Spain I work remotely, over video calls and email.
Guide (in Spanish) · reviewed on 12 October 2026
Which ADER grants can cover part of a software project, what costs they include, deadlines and what to check before hiring.
Read the guideAnother question? Write to hola@mjdevs.com.
It depends on the scope: screens and features, integrations with other systems, number of users and deadlines. That is why I don’t publish fixed rates. After a first conversation, free and with no commitment, you get a written fixed quote with scope and timeline.
A simple tool can be ready in a few weeks; a larger project is split into phases. I work in short iterations so you see real progress from the start.
Yes. I am based in Logroño and meet clients in person in La Rioja and nearby. With the rest of Spain I work remotely, over video calls and email.
I will tell you. If an off-the-shelf tool covers what you need, it is usually cheaper to use it. Custom software pays off when your processes don’t fit what is on the market or when you need several tools to work together.
I launch the application, show you how to use it and stay available for fixes, improvements and maintenance. Maintenance terms are agreed in the quote.
I'll get back to you within 48 hours with the next steps.
Request sent
Thanks for reaching out. I'll get back to you within 48 hours with the next steps.
