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Jonathan Jiménez Reina
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Portrait of Jonathan Jiménez ReinaSenior Android Engineer
based in Cádiz, Spain, working remotely

I build complete products, from architecture to the app stores.

Android engineer with more than six years of experience in Kotlin and Jetpack Compose, on apps for Real Madrid, Atresmedia, Inditex and GPS Insight. Outside that work I design, build and maintain my own apps with Kotlin Multiplatform, published on Google Play and the App Store.

See projectsWork with meDownload CV

Open to new roles and projects

  1. Architecture

    Modules with boundaries the build enforces, and decisions in writing.

  2. Code

    Kotlin shared between Android and iOS, with Compose.

  3. Tests

    Tests and quality gates before every change.

  4. Stores

    Published and maintained. See all my apps:

    Google PlayApp Store
Years in Android
6+
Apps of my own on Google Play
54 on iOS
Active users on RentaClara
500+
Crash-free users at GPS Insight
99%

They have trusted my work

Projects

Four projects I have taken from start to finish, published and in use. Client work for my employers is in the experience section; that code is not mine to show.

Dustrek

My own product, on the stores since October 2026

Motorcycle navigation for places without signal.

An app for riding trails and dirt roads, alone or in a group. It sits on the handlebars, works with gloves on, and everything important works without internet: maps for around 350 countries and regions, live group riding with crash alerts, and Bluetooth beacons for when nobody has signal.

  • The build enforces the architecture. 30 modules and custom detekt rules that break the build if anyone skips a dependency rule.
  • Offline maps without being tied to the library. MapLibre behind my own API, with PMTiles tiles downloaded by byte ranges.
  • iOS in the quality gate from day one. Only four Swift files; the rest is shared Kotlin.
new users a month
~250
modules
30
test files
769
Read the case study: DustrekGoogle Play: DustrekApp Store: Dustrekdustrek.com

  • The group, live on the map

  • Who is ahead and who is behind

  • Route panel with elevation profile

  • Bike-down alert

  • Route details

  • Offline maps

RentaClara

My own product, in production since early 2026

Rentals without spreadsheets, with an assistant that understands your numbers.

For landlords with two to ten rented properties: leases, tenants, payments, expenses, real returns and the tax paperwork. ClaraAI reads and changes your data with 50 tools, and before changing anything it shows you what it is about to do and waits for your approval.

  • Several AI providers behind a single interface. Anthropic, Gemini and DeepSeek, with automatic fallback and spending controlled on the server.
  • It works offline. Data lives on the phone and is refreshed in the background.
  • An admin panel that can't break anything. Read-only; anything that affects real users asks you to type PROD, and the server checks it again.
active users
500+
platforms
3
automated tests
2,200+
Read the case study: RentaClaraGoogle Play: RentaClaraApp Store: RentaClararentaclara.es

  • Home: the month at a glance

  • ClaraAI asks for approval

  • Real returns for one property

  • Tax report

  • Rent update with the official index

  • Payments, month by month

Rugu·Map

Commissioned by ICMAN-CSIC, citizen science

An app that lets anyone help monitor an invasive seaweed.

For the Andalusian Institute of Marine Sciences: anyone walking along the coast can record in under a minute where the Asian seaweed is piling up, even without signal. Scientists study the data in a dashboard with a heatmap, a PDF report and export to CSV, GeoJSON and KML.

  • An offline queue that never loses anything. Pending reports are written atomically and recovered even if the app is closed halfway through.
  • Camera-only photos. So the place and time are real. It is scientific data, not a pretty picture.
  • A dashboard with no server of its own. A static site talking to CSIC's server; the institute doesn't depend on me.
people signed up
250+
languages
5
steps to record
4
Read the case study: Rugu·MapGoogle Play: Rugu·MapApp Store: Rugu·Map

  • The map of reports

  • Step 1: sand or water?

  • Step 2: compare with photos

  • A single report

  • Satellite view

Sosiego

Freelance, in production at two clinics

From one clinic's project to a template for many.

Scheduling, patients, signed consent forms and WhatsApp reminders for small clinics, with a booking site for their patients. It started with Venus Estética, continued with Clínica Casín Casasola, and today it is a template for new clinics.

  • One project per clinic. One clinic's medical records never share a database with another's.
  • Privacy by specialty, enforced on the server. Psychology notes are only visible to the right people, with special rules for minors.
  • Built to cost almost nothing. It disconnects idle sessions; a typical clinic fits in Firebase's free tier.
clinics in production
2
specialties at Casín
6
Firebase bill for a typical clinic
€0
Read the case study: SosiegoTry the demo

  • Weekly schedule, by practitioner and room

  • Booking site for patients

  • Home: the clinic's day

  • The same dashboard, on a phone

Also on the stores

Two smaller apps I still maintain, and everything else I have published.

My apps on Google PlayMy apps on the App Store

How I work

I work the same way at a football club as on my own projects. These are the habits that show most in the result.

Ask me about…

Topics I know well and can explain in depth in an interview.

  • Why Dustrek downloads its own map tiles instead of using MapLibre's offline storage.
  • How phones in a group share their positions over Bluetooth when there is no internet.
  • How ClaraAI switches AI providers without the user noticing.
  • How to migrate a production server with four minutes of downtime.
  • How to migrate from Views to Compose without dropping below 85 % test coverage.

What I work with

Android
Kotlin, Jetpack Compose, Material 3, Coroutines and Flow, Hilt, Room, DataStore, Android TV
Multiplatform
Kotlin Multiplatform, Compose Multiplatform, Koin, Ktor, MapLibre
Architecture
MVVM and MVI, Clean Architecture, Modularisation, Offline-first
Quality and delivery
JUnit, Espresso, MockK, Screenshot tests, detekt, CI/CD, Play Console, App Store Connect
Backend and web
Supabase, Firebase, PocketBase, Next.js, React, TypeScript, Cloudflare Workers
AI
Claude Code, GitHub Copilot, Cursor, Anthropic, Gemini and DeepSeek APIs

Experience

More than six years in Android, always remote, on apps used by a lot of people.

  1. May 2026 – presentRemote

    Senior Android Engineer

    Knowmad Mood, for Atresmedia

    Mobile and Android TV apps for one of Spain's largest media groups. I adapt the interface and navigation to the remote control and the living-room experience.

    • Mobile and Android TV

  2. October 2024 – April 2026Remote

    Senior Android Engineer

    Softtek, for Real Madrid

    The club's official app, with live scores and coverage for millions of fans. I made architecture decisions and migrated screens from Views to Jetpack Compose without dropping below 85 % test coverage.

    • 85 % test coverage
    • Views to Compose

  3. October 2022 – October 2024Remote, for an Ireland-based company

    Senior Android Engineer

    GPS Insight

    I led the GPS Insight Driver App from scratch: architecture (MVVM, Clean Architecture, modularisation), a CI/CD pipeline with automated tests, and distribution through Firebase and Play Console. I also migrated FieldAware from Java to Kotlin and supported the team through the change.

    • 99 % crash-free users
    • Led the app from scratch

  4. March – October 2022Remote

    Senior Android Engineer

    Passporter

    I led Android development at a travel startup: Kotlin, MVVM, Clean Architecture and an offline-first cache over REST APIs.

  5. June 2020 – March 2022Remote

    Android Engineer

    NTT DATA, for Inditex

    Internal logistics app to track shipments between stores and warehouses in real time, with unit and UI tests (JUnit, Espresso).

  6. 2016 – 2020

    BSc in Software Engineering

    University of Huelva

Got an idea, or an app that needs help?

I work with companies, institutions and small businesses. I can build an app from scratch or take over one that already exists. I'll tell you what I'd do, how much it costs and when it will be ready, and I'll show you progress every week.

  • Mobile apps

    Native Android with Kotlin and Jetpack Compose, or Android and iOS together with Kotlin Multiplatform. I also handle publishing on Google Play and the App Store.

  • Web apps and admin dashboards

    Tools for running a business day to day: scheduling, bookings, customers, reports. Built with React and Next.js, on Firebase or Supabase.

  • From idea to app store

    A minimum product, done well, in the hands of real users within a few weeks and ready to grow.

  • Android app rescue

    Java to Kotlin and Views to Compose, a cleaner architecture, tests and CI. It's what I did at GPS Insight and Real Madrid.

How we work together

  1. A callYou tell me what you need; I ask whatever I need to know. No commitment.
  2. A fixed proposalWhat's included, what isn't, the price and the dates.
  3. Progress every weekA version you can try on your phone or in your browser.
  4. Launch and afterI publish it, show you how to use it and stay available to maintain it.

Want to see what it looks like? Try a real admin dashboardwith test data.

What clients say

Translated from Spanish.

“We needed anyone to be able to record a seaweed stranding in under a minute, even without signal. Rugu·Map does that, and the dashboard gives us the data ready to work with.”

Sara Haro PáezPrincipal investigator of the RoGEO project, ICMAN-CSIC

“We are six specialties sharing one schedule. Jonathan understood how we work and built a tool made for us. What we like most are the WhatsApp reminders: patients confirm their appointment with one tap.”

CristinaOwner of Clínica Casín Casasola

“Now I manage appointments, clients and consent forms from my phone, and the WhatsApp reminders go out on their own.”

Lourdes GutiérrezVenus Estética
Jonathan Jiménez Reina

About me

I'm from Seville and live in Cádiz. I studied Software Engineering at the University of Huelva, and since 2020 I've worked on Android, almost always remotely and almost always on apps used by a lot of people.

Many of my apps come from what I do outside work. I ride motorcycles on trails and dirt roads, and that's where Dustrek came from. I love sport in general, and tennis gave me Tennis Strings. Others come from someone else's real problem: RentaClara comes from landlords who manage their rentals in spreadsheets until the spreadsheets fall short.

Where
Cádiz, Spain
How
Remote since 2020
Languages
Spanish, professional English and basic French
Courses
KMP and Compose Multiplatform (2024), Firebase for Android (2023), Jetpack Compose (2022)

Let's talk

If you're looking for an Android engineer for your team or have a project in mind, drop me a line. I reply within one or two days.

Email me

Or find me here

CV